Method for preventing sewage from overflowing reversely by adopting overflow pipe in sewer of residential building

Abstract

The invention provides a method for preventing sewage from overflowing reversely through an overflow pipe in a sewer of a residential building, and belongs to the technical field of buildings. An overflow channel is triggered to be opened in advance according to the water level rising speed by matching with a double-probe ultrasonic liquid level monitoring assembly, meanwhile, a ventilation vertical pipe is arranged to balance the pressure difference of all floors, a water seal type anti-backflow valve assembly is installed at the bottom to form double protection, and an automatic air adjusting valve and a vacuum breaker are arranged on an overflow pipeline to guarantee smooth drainage. The technical problem that sewage overflows back to low-floor residents due to overload of a main drainage vertical pipe during rainstorm or water peak of a residential building drainage system is solved.

Description

Technical Field

[0001] This invention belongs to the field of building technology, and specifically relates to a method for preventing sewage backflow in residential building sewers using overflow pipes. Background Technology

[0002] Residential building drainage systems typically use a single main drainage riser to collect domestic sewage from each floor and discharge it into the municipal pipe network, which can meet drainage needs under normal water usage conditions. Traditional backflow prevention measures mainly include increasing the diameter of the main drainage riser, installing mechanical booster pumps, or installing one-way check valves. However, increasing the pipe diameter is limited by building space and has high construction and renovation costs; mechanical booster pumps rely on electricity, which poses a risk of power outages and requires frequent maintenance; and one-way check valves can only block backflow but cannot solve the problem of pressure accumulation in the upstream pipe. During periods of frequent urban rainstorms and peak water usage, the instantaneous flow surge in the main drainage riser causes the bottom pressure to rise rapidly to 80-120 kPa, far exceeding the design pressure capacity of the lower-floor drainage branch pipes (20-30 kPa). This pressure difference directly breaks the water seal of the sanitary fixture traps and causes backflow into the rooms. Traditional technical measures are unable to release the pipe pressure in time due to delayed response or insufficient diversion capacity. In other words, existing technologies present a technical problem where sewage backflows to lower-floor residents due to overload of the main drainage riser during rainstorms or peak water usage. Summary of the Invention

[0003] In view of this, the present invention provides a method for preventing sewage backflow in residential building sewers using overflow pipes, which can solve the technical problem in the prior art where sewage backflows to lower-floor residents due to overload of the main drainage riser during heavy rain or peak water usage.

[0004] The invention is implemented as follows: This invention provides a method for preventing sewage backflow in residential building sewers using overflow pipes. An overflow interface is opened at a height of 0.8 to 1.2 meters from the bottom of the main drainage riser, and a Venturi-boosted overflow assembly is installed. A dual-probe ultrasonic level monitoring assembly is installed at a height of 1.5 to 2 meters from the bottom of the main drainage riser. Based on the water level data collected by the dual-probe ultrasonic level monitoring assembly, the water level rise rate is calculated using a set of equations. Based on the water level rise rate, a rapid or slow water level rise condition is determined, and the overflow channel of the Venturi-boosted overflow assembly is opened. An automatic air regulating valve is installed at the top of the throat of the Venturi-boosted overflow assembly. A vacuum breaker is installed at the end of the overflow pipe. Ventilation riser connection points are set every 5 to 8 floors along the main drainage riser. A water-sealed anti-backflow valve assembly is installed at the connection points between the drainage branch pipes on the first floor and in the basement and the main drainage riser.

[0005] The Venturi booster overflow assembly has a contraction section inlet diameter that matches the inner diameter of the main drainage riser, a throat diameter that is 0.6 to 0.7 times the contraction section inlet diameter, and a throat length that is 2 to 3 times the throat diameter.

[0006] The upper probe of the dual-probe ultrasonic liquid level monitoring component is installed 80 to 120 mm above the warning water level line, and the lower probe is installed at the warning water level line. The vertical distance between the upper and lower probes is 80 to 120 mm.

[0007] Among them, when the water level rise rate is greater than 15 mm / min, it is judged as a rapid water level rise condition, and when the water level rise rate is less than or equal to 15 mm / min, it is judged as a slow water level rise condition.

[0008] Specifically, the overflow channel is opened when the water level is determined to be rising rapidly and the lower probe detects that the water level has reached the warning level. The overflow channel is opened when the water level is determined to be rising slowly and the upper probe detects that the water level exceeds the warning level by 60 to 80 mm.

[0009] Specifically, when the internal pressure of the overflow pipe is lower than -2 kPa, the automatic air regulating valve opens the intake mode; when the internal pressure of the overflow pipe is higher than +1 kPa, the automatic air regulating valve opens the exhaust mode.

[0010] The vacuum breaker is installed at the end of the overflow pipe, 0.3 to 0.5 meters away from the inlet of the backup drainage pipe, and the activation negative pressure threshold is -1.5 to -3 kPa.

[0011] The ventilator is connected to the atmosphere at the top and to the main drainage riser at the bottom. The inner diameter of the ventilator is 0.3 to 0.4 times that of the main drainage riser.

[0012] The equation set for calculating the rate of water level rise includes the equation for the rate of water level rise, the equation for the overflow initiation prediction time, and the equation for the negative pressure at the Venturi throat.

[0013] The equation for the rate of water level rise is expressed as follows: the ratio of the rate of water level rise to 15 mm / min is equal to the ratio of the difference between the water level data of the upper probe and the water level data of the lower probe, divided by the quotient of the difference between the vertical distance between the upper and lower probes, divided by 0.15.

[0014] The overflow start prediction time equation is expressed as follows: the overflow start prediction time divided by 1 minute is equal to the ratio of the difference between the warning water level height and the lower probe water level data, divided by the quotient of the water level rise rate, divided by 15. The numerical range of the overflow start prediction time is 0.5 to 2.

[0015] The Venturi throat negative pressure equation is expressed as follows: the ratio of the throat negative pressure value divided by 20 kPa is equal to the ratio of the main drainage riser flow velocity divided by 1 m / s multiplied by the quotient of the contraction section inlet diameter divided by the throat diameter minus 1, and the difference divided by 0.5. The numerical range of the throat negative pressure value is 15 to 25.

[0016] The Venturi booster overflow assembly has a contraction section length of 1.5 to 2 times the inlet diameter of the contraction section, a diffuser section length of 3 to 5 times the outlet diameter of the diffuser section, a cone angle of 15 to 20 degrees for the contraction section, and a cone angle of 6 to 8 degrees for the diffuser section.

[0017] The water-sealed anti-backflow valve assembly includes a valve body, a water seal chamber, and a spring-loaded valve disc. The water seal chamber has a depth of 50 mm and a pressure-bearing capacity of 150 kPa.

[0018] Among them, when the sewage in the main drainage riser of the Venturi booster overflow component flows through the contraction section, the flow velocity increases, resulting in a pressure reduction of 15 to 25 kPa at the throat. The overflow branch pipe interface opened at the throat automatically draws sewage into the backup drainage pipe under the action of negative pressure suction, and the suction flow rate accounts for 20% to 35% of the main pipe flow rate.

[0019] Among them, the dual-probe ultrasonic liquid level monitoring component calculates the rate of water level rise by the difference between the water levels of the upper and lower probes, predicts the peak water level 0.5 to 2 minutes in advance and triggers the overflow start signal, with a measurement frequency of 6 to 10 times per minute.

[0020] This invention utilizes a Venturi-style pressure-boosting overflow assembly installed at a specific height on the main drainage riser. This assembly leverages the increased flow velocity of sewage as it flows through the contraction section, generating negative pressure at the throat to automatically draw 20% to 35% of the sewage into a backup drainage pipe. This achieves passive diversion without external power. Simultaneously, a dual-probe ultrasonic level monitoring assembly differentiates between rapid and slow water level rises and preemptively triggers the overflow channel to prevent water levels from exceeding warning levels. The Venturi throat negative pressure automatically matches the main pipe flow rate, allowing the diversion flow to adjust synchronously with the drainage load. During heavy rain, when the main pipe flow velocity increases, the throat negative pressure synchronously rises to 15 to 25 kPa, increasing the suction flow and effectively reducing the rate of pressure accumulation at the bottom. Combined with a vented riser balancing the pressure difference between floors and a water-sealed anti-backflow valve providing dual protection, backflow paths caused by pressure surges are eliminated. In summary, this invention solves the technical problem mentioned in the background art: sewage backflow into lower-floor residents' homes due to overload of the main drainage riser during heavy rain or peak water usage. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method of the present invention.

[0022] Figure 2The present invention relates to a drainage overflow structure, including two sub-figures: (A) is a schematic diagram of a single-pipe drainage pipe structure, and (B) is a schematic diagram of a double-pipe drainage pipe structure.

[0023] Figure 3 Detailed structure of the Venturi booster overflow assembly.

[0024] Figure 4 It is a water-sealed anti-backflow valve assembly structure.

[0025] Figure 5 This is a schematic diagram of the single-pipe drainage pipe structure design in the embodiment.

[0026] Figure 6 This is a schematic diagram of the double-pipe drainage pipe structure design in the embodiment. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0028] like Figure 1 The diagram shown is a flowchart of a method for preventing sewage backflow in residential building sewers using an overflow pipe, provided by the present invention. This method includes the following steps:

[0029] S10. An overflow interface is opened at a height of 0.8 to 1.2 meters from the bottom of the main drainage riser, and a Venturi pressure-boosting overflow assembly is installed. The inlet diameter of the constriction section of the Venturi pressure-boosting overflow assembly is consistent with the inner diameter of the main drainage riser, the throat diameter is 0.6 to 0.7 times the inlet diameter of the constriction section, and the throat length is 2 to 3 times the throat diameter.

[0030] S20. Install a dual-probe ultrasonic liquid level monitoring component at a height of 1.5 to 2 meters from the bottom inside the main drainage riser. The upper probe is installed 80 to 120 mm above the warning water level line, and the lower probe is installed at the warning water level line. The vertical distance between the upper probe and the lower probe is 80 to 120 mm.

[0031] S30. Based on the water level data of the upper probe and the lower probe collected by the dual-probe ultrasonic liquid level monitoring component, the water level rise rate and overflow start prediction time are calculated by the water level rise rate calculation equation set. When the water level rise rate is greater than 15 mm / min, it is determined to be a rapid water level rise condition. When the water level rise rate is less than or equal to 15 mm / min, it is determined to be a slow water level rise condition.

[0032] S40. When the condition is determined to be a rapid water level rise and the lower probe detects that the water level has reached the warning water level line, the overflow channel of the Venturi booster overflow component is opened to divert the sewage in the main drainage riser to the backup drainage pipe. When the condition is determined to be a slow water level rise and the upper probe detects that the water level exceeds the warning water level line by 60 to 80 mm, the overflow channel is opened.

[0033] S50. An automatic air regulating valve is installed at the top of the throat of the Venturi booster overflow assembly. When the internal pressure of the overflow pipe is lower than -2kPa, the automatic air regulating valve opens the intake mode. When the internal pressure of the overflow pipe is higher than +1kPa, the automatic air regulating valve opens the exhaust mode. A vacuum breaker is installed at the end of the overflow pipe at a distance of 0.3 to 0.5 meters from the inlet of the backup drainage pipe.

[0034] S60. Ventilation riser connection points are set at the height of the main drainage riser every 5 to 8 floors. The top of the ventilation riser is connected to the atmosphere and the bottom is connected to the main drainage riser. The inner diameter of the ventilation riser is 0.3 to 0.4 times the inner diameter of the main drainage riser. Water seal anti-backflow valve assemblies are installed at the connection between the drainage branch pipes on the first floor and the basement and the main drainage riser.

[0035] The Venturi pressure-boosting overflow component is a device that utilizes the Venturi effect to achieve automatic diversion without power. When sewage flows through the contraction section in the main drainage riser, the increased flow velocity causes a pressure drop of 15 to 25 kPa at the throat. The overflow branch pipe interface at the throat automatically draws sewage into the backup drainage pipe under the action of negative pressure suction. The suction flow rate accounts for 20% to 35% of the main pipe flow rate, and the suction volume is automatically matched with the main pipe flow rate. The length of the contraction section of the Venturi pressure-boosting overflow component is 1.5 to 2 times the diameter of the inlet of the contraction section, and the length of the diffuser section is 3 to 5 times the diameter of the outlet of the diffuser section. The outlet diameter of the diffuser section is restored to the inner diameter of the main drainage riser. The cone angle of the contraction section is 15 to 20 degrees, and the cone angle of the diffuser section is 6 to 8 degrees.

[0036] The dual-probe ultrasonic liquid level monitoring component calculates the rate of water level rise by the difference between the water levels of the upper and lower probes, predicts the peak water level 0.5 to 2 minutes in advance and triggers the overflow start signal, and achieves a control accuracy within the range of ±5mm. The measurement frequency of the dual-probe ultrasonic liquid level monitoring component is 6 to 10 times per minute.

[0037] The equation set for calculating the rate of water level rise includes the equation for the rate of water level rise, the equation for the overflow initiation prediction time, and the equation for the negative pressure at the Venturi throat.

[0038] The water level rise rate equation is used to calculate the rate of water level rise in the main drainage riser. The inputs include the water level data of the upper probe, the water level data of the lower probe, and the vertical distance between the upper and lower probes. The output is the water level rise rate. The water level rise rate equation is expressed as follows: the ratio of the water level rise rate divided by 15 mm / min is equal to the ratio of the difference between the water level data of the upper probe and the water level data of the lower probe divided by the quotient of the vertical distance between the upper and lower probes divided by 0.15. The units of the water level data of the upper probe are mm, the units of the water level data of the lower probe are mm, and the units of the vertical distance between the upper and lower probes are mm.

[0039] The overflow initiation prediction time equation is used to calculate the prediction time before the overflow channel opens. The inputs include the warning water level height, the lower probe water level data, and the water level rise rate. The output is the overflow initiation prediction time. The overflow initiation prediction time equation is expressed as follows: the overflow initiation prediction time divided by 1 minute is equal to the ratio of the difference between the warning water level height and the lower probe water level data, divided by the water level rise rate, divided by 15. The unit of the warning water level height is mm, the unit of the overflow initiation prediction time is minus minutes, and the numerical range of the overflow initiation prediction time is 0.5 to 2.

[0040] The Venturi throat negative pressure equation is used to calculate the negative pressure value at the throat position of the Venturi booster overflow component. The inputs include the main drainage riser flow velocity, the throat diameter, and the contraction section inlet diameter. The output is the throat negative pressure value. The Venturi throat negative pressure equation is expressed as follows: the ratio of the throat negative pressure value to 20 kPa is equal to the ratio of the main drainage riser flow velocity to 1 m / s multiplied by the quotient of the contraction section inlet diameter divided by the throat diameter minus 1, and the difference divided by 0.5. The unit of the main drainage riser flow velocity is m / s, the unit of the throat negative pressure value is kPa, and the numerical range of the throat negative pressure value is 15 to 25.

[0041] The automatic air regulating valve is a two-way pressure regulating device. The intake mode is used to prevent air from being unable to be discharged in time when the overflow pipe drains quickly, forming an airlock that obstructs the water flow. The exhaust mode is used to prevent excessive air accumulation in the overflow pipe from affecting the flow capacity. The opening pressure threshold of the automatic air regulating valve is determined according to the diameter and length of the overflow pipe.

[0042] The vacuum breaker is an anti-siphon device. When the overflow pipe finishes draining and a negative pressure is formed in the pipe, creating a siphon effect, the vacuum breaker automatically introduces air to break the siphon, avoiding excessive water level drop in the main drainage riser due to continuous suction. The starting negative pressure threshold of the vacuum breaker is -1.5 to -3 kPa.

[0043] The water-sealed anti-backflow valve assembly includes a valve body, a water seal chamber, and a spring-loaded pressure valve disc. The water seal chamber has a depth of 50mm. During normal drainage, the water flow opens the spring-loaded pressure valve disc. When backflow occurs due to high-rise drainage pressure, the water seal chamber isolates the airflow, and the spring-loaded pressure valve disc is pressed tight under the spring force, achieving a pressure resistance of 150kPa. The water-sealed anti-backflow valve assembly, together with the water trap installed on the drainage branch pipe, forms a double protection. The water seal depth of the water trap is 60 to 80mm.

[0044] The ventilation riser forms a dual-riser ventilation system, which balances the pressure difference between floors of the main drainage riser through air flow. This prevents pressure shocks to the drainage branch pipes on lower floors when the pressure at the bottom of the main drainage riser in a high-rise building reaches 80 to 120 kPa. The design pressure of the drainage branch pipes on lower floors is 20 to 30 kPa. The risk of backflow caused by pressure difference is eliminated by the pressure balancing effect of the ventilation riser.

[0045] The rapid water level rise condition corresponds to heavy rain or peak water usage periods. When the water level rise rate is greater than 15 mm / min, the overflow needs to be started in advance to prevent the water level from exceeding the warning water level line. The slow water level rise condition corresponds to daily water usage periods. The overflow is allowed to be started after the water level rises to 60 to 80 mm above the warning water level line in order to save the backup drainage capacity.

[0046] The overflow channel is opened by an electric regulating valve or a pneumatic regulating valve. The electric regulating valve or the pneumatic regulating valve receives the control signal output by the dual-probe ultrasonic liquid level monitoring component, and the response time is 3 to 8 seconds. The overflow capacity of the overflow channel is determined according to the design flow rate of the main drainage riser, and the overflow diversion ratio is 20% to 35% of the main pipeline flow rate.

[0047] The backup drainage pipe is connected to a municipal backup drainage well or a temporary storage device. The municipal backup drainage well is 3 to 8 meters deep. The water level difference between the main drainage riser and the municipal backup drainage well is used as the overflow driving force. The volume of the temporary storage device is determined according to the number of residents in the community and the duration of peak water use. The volume of the temporary storage device is 1.5 to 2 times the design flow rate of the main drainage riser in 1 hour.

[0048] The upper probe water level data is the distance between the water level in the main drainage riser detected by the upper probe at the measurement time and the bottom of the main drainage riser. The lower probe water level data is the distance between the water level in the main drainage riser detected by the lower probe at the measurement time and the bottom of the main drainage riser. The warning water level line height is the distance between the preset maximum allowable safe water level in the main drainage riser and the bottom of the main drainage riser. The warning water level line height is determined according to the design parameters of the main drainage riser and the bearing capacity of the drainage system.

[0049] The flow velocity in the main drainage riser is obtained by dividing the instantaneous flow rate of the main drainage riser by the cross-sectional area of ​​the main drainage riser. The instantaneous flow rate of the main drainage riser is measured by a flow meter installed on the main drainage riser at a height of 0.3 to 0.5 meters from the bottom of the main drainage riser.

[0050] The overflow pipe is a pipe connecting the throat overflow branch pipe interface of the Venturi booster overflow assembly to the standby drainage pipe. The inner diameter of the overflow pipe is 0.4 to 0.6 times the inner diameter of the main drainage riser. The filling degree of the overflow pipe is controlled below 0.7, leaving sufficient air circulation space.

[0051] The suction flow rate is the sewage flow rate drawn from the main drainage riser into the backup drainage pipe by the negative pressure suction of the throat of the Venturi booster overflow component. The suction flow rate is directly proportional to the flow velocity of the main drainage riser. The greater the flow velocity of the main drainage riser, the greater the suction flow rate, thus realizing the automatic flow matching function.

[0052] The specific implementation methods of the above steps are described in detail below.

[0053] The specific implementation of step S10 is as follows: First, determine the inner diameter and bottom reference position of the main drainage riser. Mark the installation position of the overflow interface at a height of 0.8 to 1.2 meters from the bottom using a measuring tool. Use a cutting tool to create a circular hole at the marked position, with the hole diameter matching the inlet diameter of the contraction section of the Venturi booster overflow assembly. When installing the Venturi booster overflow assembly, connect the contraction section inlet flange to the created hole and tighten it with bolts, ensuring that the contraction section inlet diameter is completely consistent with the inner diameter of the main drainage riser to avoid generating additional flow resistance. Based on Bernoulli's principle and the continuity equation, determine that the throat diameter is 0.6 to 0.7 times the inlet diameter of the contraction section, and the throat length is set to 2 to 3 times the throat diameter to ensure that the flow velocity in the throat region is sufficiently increased and the pressure is stably reduced. A throat length that is too short will result in insufficient pressure reduction, while a throat length that is too long will increase head loss. The cone angle of the contraction section is controlled between 15 and 20 degrees to avoid water flow separation and the formation of eddies. The cone angle of the diffusion section is controlled between 6 and 8 degrees to achieve pressure recovery while preventing excessive energy loss. The Venturi pressure-boosting overflow assembly achieves the function of automatically sucking up overflow without external power through the optimized design of its geometry.

[0054] The specific implementation of step S20 involves installing a fixed bracket for the dual-probe ultrasonic level monitoring component on the inner wall of the main drainage riser at a height of 1.5 to 2 meters from the bottom. The fixed bracket is made of stainless steel to prevent corrosion. The lower probe is installed at the warning water level line, the position of which is predetermined based on the design capacity of the main drainage riser and the load-bearing capacity of the drainage system, typically set at 70% to 80% of the effective height of the main drainage riser. The upper probe is installed 80 to 120 mm above the lower probe. The vertical distance between the upper and lower probes directly affects the accuracy of the water level rise rate calculation; too small a distance will amplify the measurement error, while too large a distance will reduce the response sensitivity. A distance of 100 mm is preferred for actual installation. The measurement frequency of the dual-probe ultrasonic level monitoring component is set to 6 to 10 times per minute. Real-time water level change trends are obtained through high-frequency sampling. The ultrasonic measurement principle is based on calculating the water level height based on the reflection time difference of sound waves at the air-water interface, achieving a measurement accuracy within ±5 mm, which meets the precise control requirements for overflow initiation.

[0055] The specific implementation of step S30 involves real-time acquisition of water level data from the upper and lower probes using a dual-probe ultrasonic level monitoring component. The acquired water level data is then input into a set of equations for calculating the water level rise rate. The inputs to the water level rise rate equations include the water level data from the upper probe, the water level data from the lower probe, and the vertical distance between the upper and lower probes. The output is the water level rise rate, calculated as the ratio of the difference in water levels between the two probes to the vertical distance, and normalized to eliminate dimensional interference. The inputs to the overflow initiation prediction time equations include the warning water level line height, the water level data from the lower probe, and the water level rise rate. The output is the overflow initiation prediction time, which represents the time difference between the current water level and the warning water level line, used to initiate the overflow system in advance. The Venturi throat negative pressure equation takes into account the main drainage riser flow velocity, throat diameter, and contraction section inlet diameter. The output is the throat negative pressure value, calculated based on the square of the flow velocity to diameter ratio. Higher flow velocities or larger diameter contraction ratios result in higher negative pressure values. The judgment logic is as follows: a calculated water level rise rate greater than 15 mm / min is considered a rapid water level rise condition; a rate less than or equal to 15 mm / min is considered a slow water level rise condition. The threshold of 15 mm / min is an empirical value corresponding to typical water level changes during heavy rain or peak water usage periods.

[0056] The specific implementation of step S40 involves determining the timing of the overflow channel opening based on the operating condition type determined in step S30 and the water level monitoring data. When a rapid water level rise condition is determined, the control system continuously monitors the water level data from the lower probe. Once the lower probe detects that the water level has reached the warning water level line, it immediately sends an opening signal to the electric regulating valve or the pneumatic regulating valve. The response time of the opening signal is 3 to 8 seconds. The electric regulating valve opens by a motor driving the valve, and the pneumatic regulating valve opens by compressed air pushing the piston. Both types of regulating valves achieve rapid opening of the overflow channel. When a slow water level rise condition is determined, the control system monitors the water level data from the upper probe. An opening signal is only sent when the upper probe detects that the water level exceeds the warning water level line by 60 to 80 mm. This delayed opening strategy is used to save backup drainage capacity and avoid frequent activation of the overflow system. After the overflow channel is opened, the sewage in the main drainage riser is drawn into the backup drainage pipe under the negative pressure suction of the throat of the Venturi pressurized overflow component. The suction flow rate accounts for 20% to 35% of the main pipe flow rate. The suction flow rate is automatically matched with the main pipe flow rate. The larger the flow rate, the stronger the negative pressure and the greater the suction volume, thus realizing the adaptive diversion function.

[0057] The specific implementation of step S50 involves welding or threading an automatic air regulating valve to the top of the throat of the Venturi pressure-boosting overflow assembly. The automatic air regulating valve includes a pressure sensor and a bidirectional pneumatic valve. The pressure sensor monitors the internal pressure of the overflow pipe in real time. When the overflow pipe drains water rapidly, the air inside the pipe is squeezed out by the water flow at a slower rate than the water flow, causing the internal pressure to drop below -2 kPa, forming an airlock that obstructs the water flow. At this time, the automatic air regulating valve activates its intake mode, drawing in air from the outside to replenish the gas pressure inside the pipe and prevent airlock formation. When too much air accumulates in the overflow pipe, the internal pressure exceeds +1 kPa, affecting the flow capacity. The automatic air regulating valve then activates its exhaust mode to expel the excess air and restore normal hydraulic conditions. A vacuum breaker is installed at the end of the overflow pipe, 0.3 to 0.5 meters away from the inlet of the backup drainage pipe. The vacuum breaker is a mechanical one-way valve structure. When the overflow pipe finishes draining and the water column in the pipe falls to form a siphon negative pressure, the vacuum breaker automatically opens under the negative pressure to introduce air and break the siphon effect, preventing continuous suction from causing the water level in the main drainage riser to drop excessively or even pumping up the bottom sediment and causing pipe blockage. The starting negative pressure threshold of the vacuum breaker is -1.5 to -3 kPa.

[0058] The specific implementation of step S60 involves opening venting riser connection holes every 5 to 8 floors along the main drainage riser. The inner diameter of the venting riser is 0.3 to 0.4 times that of the main drainage riser. The top of the venting riser extends to the building roof to connect with the atmosphere, and the bottom connects to the main drainage riser to form a dual-riser venting system. The venting riser achieves pressure balance across floors through airflow. When drainage occurs in higher floors, the pressure in the main drainage riser increases, and the venting riser automatically introduces air to reduce the pressure. When drainage occurs in lower floors, the venting riser discharges air to replenish the pressure, preventing pressure shocks to the lower-floor drainage branch pipes, which are designed to withstand only 20 to 30 kPa, when the pressure at the bottom of the main drainage riser in high-rise buildings reaches 80 to 120 kPa. A water-sealed anti-backflow valve assembly is installed at the connection between the drainage branch pipes on the first floor and in the basement and the main drainage riser. The valve body of the water-sealed anti-backflow valve assembly has a 50 mm deep water seal chamber, which is normally maintained in a water seal. The spring-loaded valve disc is closed under the action of the spring force. During normal drainage, the impact force of the water flow overcomes the spring force to push open the valve to achieve drainage. When the drainage pressure of the high-rise building backflows, the water seal of the water seal chamber isolates the airflow conduction. The spring-pressurized valve closes tightly under the combined action of the spring force and the backflow pressure, with a pressure bearing capacity of 150kPa. Together with the water trap with a water seal depth of 60 to 80mm installed on the drainage branch pipe, it forms a double protection, effectively preventing odor and sewage from backflowing to sanitary fixtures on lower floors.

[0059] It should be noted that the key technical concepts of this invention include Venturi effect non-powered overflow technology, dual-probe water level prediction technology, and multi-stage pressure balance protection technology. Venturi effect non-powered overflow technology optimizes the geometric parameters of the contraction section and throat, utilizing fluid dynamics principles to convert water kinetic energy into negative pressure potential energy. This generates a negative pressure suction of 15 to 25 kPa at the throat, achieving automatic suction overflow. Compared to traditional electric pump-driven overflow methods, this eliminates dependence on external power, reducing system energy consumption and maintenance costs. Furthermore, the suction flow rate automatically matches the main pipeline flow rate, naturally possessing flow following characteristics and avoiding complex flow regulation and control systems. Dual-probe water level prediction technology calculates the water level rise rate by measuring the water level difference between two probes. Based on the rate change trend, it predicts the peak water level 0.5 to 2 minutes in advance and initiates overflow. Compared to the traditional single-point level switch triggering method, this improves control accuracy from 2 to 5 cm to ±5 mm, effectively avoiding the risk of wasted overflow capacity or water level exceeding the warning line due to inaccurate start-up timing. The multi-stage pressure balancing protection technology balances the pressure difference between floors through venting risers, forming a three-stage protection system in conjunction with water-sealed anti-backflow valves and water traps. Compared to the traditional single water trap protection method, it increases the backflow pressure resistance from 30kPa to 150kPa, completely solving the problem of backflow of odors and water from sanitary fixtures on lower floors of high-rise buildings. The synergistic effect of the three technologies lies in the Venturi effect providing non-powered diversion capability, the dual-probe prediction technology ensuring the precise timing of overflow initiation, and the multi-stage pressure balancing protection technology ensuring the drainage safety of each floor. Together, they construct a highly efficient, energy-saving, responsive, safe, and reliable residential building drainage overflow protection system. Compared to the traditional drainage system that passively bears drainage pressure by relying solely on pipe diameter margin, this invention achieves active diversion control and all-round pressure protection, fundamentally solving the problem of sewage backflow during extreme weather and peak water usage periods.

[0060] It should be noted that this invention also solves the following technical problems: airlocks forming in overflow pipes during rapid drainage due to delayed air expulsion, obstructing water flow; and the siphon effect caused by negative pressure in the pipe after drainage, leading to excessive reduction in the water level of the main drainage riser. This invention addresses these problems by installing an automatic air regulating valve at the top of the throat of the Venturi-pressurized overflow assembly. When the internal pressure of the overflow pipe is below -2 kPa, the suction mode is activated to replenish air and eliminate airlocks. When the pressure is above +1 kPa, the exhaust mode is activated to release accumulated air and maintain flow capacity. Simultaneously, a vacuum breaker is installed at the end of the overflow pipe, 0.3 to 0.5 meters from the inlet of the backup drainage pipe. When a negative pressure of -1.5 to -3 kPa forms in the pipe after drainage, air is automatically introduced to break the siphon, preventing abnormal fluctuations in the main pipe water level caused by continuous suction. The combination of the bidirectional pressure regulating device and the anti-siphon device ensures that the overflow pipe maintains a gas-liquid two-phase flow balance during dynamic drainage.

[0061] Specifically, the principle of this invention is as follows: The fundamental principle behind the solution to the overload overflow problem of the main drainage riser lies in the synergistic effect of the adaptive flow passive diversion mechanism and the pressure feedforward control system. The Venturi booster overflow component converts the kinetic energy of sewage in the pipe into negative pressure potential energy at the throat position through the hydrodynamic contraction effect. The ratio of the inlet diameter to the throat diameter of the contraction section is 0.6 to 0.7 times, and the cone angle design of the contraction section is 15 to 20 degrees. This ensures that a stable negative pressure zone of 15 to 25 kPa is formed at the throat when sewage flows through. This negative pressure value increases with the square of the flow velocity in the main pipe, thus automatically enhancing the suction capacity when the flow rate surges. Real-time matching of diversion flow and drainage load can be achieved without sensor judgment or actuator response. The dual-probe ultrasonic level monitoring component calculates the rate of water level rise by measuring the vertical distance difference of 80 to 120 mm between the upper and lower probes. It predicts the peak water level arrival time 0.5 to 2 minutes in advance and outputs an overflow start signal, activating the passive diversion mechanism in advance before the pressure critical state. This avoids the lag of traditional reactive response methods. This feedforward control logic conforms to the basic principle of rapid disturbance suppression in dynamic systems, and therefore can effectively prevent the bottom pressure from exceeding the limit under sudden conditions such as heavy rain.

[0062] The following provides a specific embodiment 1 of the present invention, and the specific implementation of each step in this embodiment 1 is described in detail below.

[0063] The specific implementation of step S10 involves opening an overflow interface and installing a Venturi booster overflow assembly at a height of 0.8 to 1.2 meters from the bottom of the main drainage riser. The inlet diameter of the constriction section of this assembly is consistent with the inner diameter of the main drainage riser to ensure a smooth water flow transition. The throat diameter is designed to be 0.6 to 0.7 times the inlet diameter of the constriction section to generate sufficient flow acceleration. The throat length is designed to be 2 to 3 times the throat diameter to ensure a sufficient negative pressure formation area. The length of the constriction section is 1.5 to 2 times the inlet diameter of the constriction section, and the length of the diffuser section is 3 to 5 times the outlet diameter of the diffuser section. The outlet diameter of the diffuser section is restored to the inner diameter of the main drainage riser to ensure smooth water flow back to the main pipeline. The cone angle of the contraction section is designed to be 15 to 20 degrees to avoid fluid separation, and the cone angle of the diffuser section is designed to be 6 to 8 degrees to reduce energy loss. The Venturi booster overflow component uses the Venturi effect to achieve automatic diversion without power. When sewage flows through the contraction section, the flow velocity increases, resulting in a pressure reduction of 15 to 25 kPa at the throat. The overflow branch pipe interface opened at the throat automatically draws sewage into the backup drainage pipeline under the action of negative pressure suction. The suction flow rate accounts for 20% to 35% of the main pipeline flow rate and is automatically matched with the main pipeline flow rate.

[0064] The specific implementation of step S20 is to install a dual-probe ultrasonic level monitoring component at a height of 1.5 to 2 meters from the bottom inside the main drainage riser. The upper probe is installed 80 to 120 mm above the warning water level line to monitor the water level change trend in advance, and the lower probe is installed at the warning water level line to determine whether the warning water level has been reached. The vertical distance between the upper and lower probes is set to 80 to 120 mm to provide sufficient water level difference resolution. The measurement frequency of the dual-probe ultrasonic level monitoring component is set to 6 to 10 times per minute to ensure real-time tracking of water level changes. The control accuracy reaches a range of ±5 mm to ensure accurate triggering of the overflow start signal.

[0065] The specific implementation of step S30 involves calculating the water level rise rate and overflow initiation prediction time based on the water level data from the upper and lower probes collected by the dual-probe ultrasonic level monitoring component, using a set of water level rise rate calculation equations. The formula for the water level rise rate equation is as follows:

[0066] ;

[0067] In the formula, This is the rate of water level rise, expressed in mm / min, with a typical range of 5 to 50 mm / min. The water level data from the upper probe is in mm, representing the distance between the water level height detected by the upper probe in the main drainage riser and the bottom of the main drainage riser at the time of measurement. The lower probe water level data, in mm, represents the distance between the water level height detected by the lower probe in the main drainage riser and the bottom of the main drainage riser at the time of measurement. The vertical distance between the upper and lower probes is expressed in mm, with a design value of 80 to 120 mm. The equation is based on the principle that the rate of water level rise is reflected by the ratio of the water level difference between the two probes at different heights at the same moment to the vertical distance. The equation eliminates dimensional effects through normalization. The numerator on the right side of the equation... The calculation measures the degree of water level filling the vertical gap. The denominator 0.15 on the right side of the equation is the normalization coefficient of the degree of water level filling corresponding to the critical values ​​of fast and slow operating conditions. The effect of the equation is to accurately reflect the rate of water level change in the main drainage riser.

[0068] The formula for the overflow start-up prediction time equation is expressed as follows:

[0069] ;

[0070] In the formula, The overflow start prediction time is given in minutes, with a value range of 0.5 to 2. The warning water level, in mm, represents the distance from the bottom of the main drainage riser to the highest permissible safe water level within the main drainage riser. It is determined based on the design parameters of the main drainage riser and the load-bearing capacity of the drainage system, with an empirical value of 1800 to 2200 mm. The equation's principle is based on predicting the time required to reach the warning water level using the ratio of the remaining height from the current water level to the rate of water level rise. The equation is normalized to achieve dimensionlessness. The numerator on the right side of the equation... The calculation is the original time required for the water level to rise from the lower probe position to the warning water level line according to the current water level rise rate. The denominator 15 on the right side of the equation is the time normalization coefficient corresponding to the critical rate of fast and slow operation. The effect of the equation is to predict the peak water level and trigger the overflow start signal 0.5 to 2 minutes in advance.

[0071] The formula for the Venturi throat negative pressure equation is as follows:

[0072] ;

[0073] In the formula, This refers to the negative pressure value in the throat, expressed in kPa, with a range of 15 to 25. The flow velocity in the main drainage riser is measured in m / s. It is obtained by dividing the instantaneous flow rate of the main drainage riser by the cross-sectional area of ​​the main drainage riser. The instantaneous flow rate of the main drainage riser is measured by a flow meter installed at a height of 0.3 to 0.5 meters from the bottom of the main drainage riser. The empirical value is 0.8 to 2 m / s. This is the inlet diameter of the contraction section, in mm, and is consistent with the inner diameter of the main drainage riser, typically ranging from 100 to 200 mm. The throat diameter, in mm, is 0.6 to 0.7 times the inlet diameter of the contraction section. The equation is based on Bernoulli's principle of the Venturi effect; the increased fluid velocity in the contraction section leads to a decrease in static pressure. The equation characterizes the intensity of the negative pressure at the throat by multiplying the flow velocity in the main drainage riser by the ratio of the pipe diameter to the flow velocity. The numerator on the right side of the equation... This reflects the combined effect of the increase in flow velocity and the pipe diameter contraction ratio. The denominator 0.5 on the right side of the equation is the normalization coefficient for the negative pressure generation efficiency. The equation's effect is to accurately calculate the negative pressure value at the throat position to ensure that the suction flow rate reaches 20% to 35% of the main pipeline flow rate. When the water level rise rate is greater than 15 mm / min, it is determined to be a rapid water level rise condition corresponding to heavy rain or peak periods of concentrated water use. When the water level rise rate is less than or equal to 15 mm / min, it is determined to be a slow water level rise condition corresponding to normal water use periods.

[0074] The specific implementation of step S40 is as follows: when a rapid water level rise is determined and the lower probe detects that the water level has reached the warning water level line, the overflow channel of the Venturi booster overflow component is immediately opened to start the overflow in advance and prevent the water level from exceeding the warning water level line. When a slow water level rise is determined and the upper probe detects that the water level exceeds the warning water level line by 60 to 80 mm, the overflow channel is opened to save backup drainage capacity. The opening of the overflow channel is controlled by an electric regulating valve or a pneumatic regulating valve and receives the control output from the dual-probe ultrasonic liquid level monitoring component. The signal has a response time of 3 to 8 seconds. The overflow channel diverts sewage from the main drainage riser to the backup drainage pipe. The overflow pipe is the pipe connecting the throat overflow branch pipe interface of the Venturi booster overflow component to the backup drainage pipe. The inner diameter of the overflow pipe is 0.4 to 0.6 times the inner diameter of the main drainage riser. The filling degree of the overflow pipe is controlled below 0.7 to reserve sufficient air circulation space. The flow capacity of the overflow channel is determined according to the design flow rate of the main drainage riser to ensure that the overflow diversion ratio is 20% to 35% of the main pipe flow rate.

[0075] The specific implementation of step S50 is to install an automatic air regulating valve at the top of the throat of the Venturi pressure-boosting overflow assembly as a two-way pressure regulating device. When the internal pressure of the overflow pipe is lower than -2 kPa, the automatic air regulating valve opens the intake mode to prevent the air in the pipe from being insufficiently discharged when the overflow pipe drains quickly, forming an air lock that obstructs the water flow. When the internal pressure of the overflow pipe is higher than +1 kPa, the automatic air regulating valve opens the exhaust mode to prevent excessive air accumulation in the overflow pipe from affecting the flow capacity. The opening pressure threshold of the automatic air regulating valve is determined according to the diameter and length of the overflow pipe. A vacuum breaker is installed at the end of the overflow pipe at a distance of 0.3 to 0.5 meters from the inlet of the backup drainage pipe as an anti-siphon device. When the overflow pipe finishes draining and a negative pressure is formed in the pipe, producing a siphon effect, the vacuum breaker automatically introduces air to break the siphon to avoid continuous suction causing excessive drop in the water level in the main drainage riser. The starting negative pressure threshold of the vacuum breaker is -1.5 to -3 kPa.

[0076] The specific implementation of step S60 is the same as described above, and will not be repeated in detail here.

[0077] To better understand and implement this invention, the following is a specific application scenario of this invention, Example 2:

[0078] A technical team undertook the task of renovating the drainage system of an 18-story high-rise residential building. The main drainage riser of the building has an inner diameter of 150mm. Due to design flaws in the original drainage system, sewage backflow frequently occurred in the sewers of first-floor residents during heavy rain and peak water usage periods. Based on the technical solution of this invention, the technical team carried out a systemic renovation of the building's drainage system. The specific implementation process is as follows.

[0079] The technical team first installed an overflow inlet 1 meter above the bottom of the main drainage riser and then installed a Venturi-style pressure-boosting overflow assembly. The inlet diameter of the constriction section of this Venturi-style pressure-boosting overflow assembly was designed to be 150mm, matching the inner diameter of the main drainage riser; the throat diameter was determined to be 95mm; and the throat length was set at 240mm. The calculated length of the constriction section was 270mm, the length of the diffuser section was set at 630mm, the outlet diameter of the diffuser section was restored to 150mm, the cone angle of the constriction section was set at 18 degrees, and the cone angle of the diffuser section was set at 7 degrees. Figure 5 As shown, in the drainage system of a residential building with an overflow pipe installed indoors, the overflow pipe is discharged to the inspection well, which is a separate discharge point on each floor. However, since the height of the overflow pipe is lower than the height of the cabinet, there is a risk of easy blockage. In addition, the alarm valve and overflow alarm device are located near the blockage-prone area, which cannot effectively prevent sewage backflow.

[0080] A dual-probe ultrasonic level monitoring unit was installed 1.8 meters above the bottom of the main drainage riser. The upper probe was installed 100 mm above the warning water level line, and the lower probe was installed at the warning water level line, which was set at a height of 1700 mm. The vertical distance between the upper and lower probes was 100 mm, and the measurement frequency was set to 8 times per minute. This monitoring unit calculates the rate of water level rise in real time by measuring the difference between the water level data from the upper and lower probes, achieving a control accuracy within ±5 mm. It can predict the peak water level 0.5 to 2 minutes in advance and trigger an overflow start signal.

[0081] The technical team integrated a set of equations for calculating the rate of water level rise into the system to distinguish between rapid and slow water level rise conditions. During a specific rainstorm, the upper sensor detected a water level of 1760 mm, and the lower sensor detected 1680 mm. The calculated rate of water level rise was 48 mm / min. Since this value was greater than 15 mm / min, the system classified it as a rapid water level rise condition. When the lower sensor detected that the water level had reached the warning level of 1700 mm, the electric regulating valve opened the overflow channel within 5 seconds, diverting sewage from the main drainage riser to the backup drainage pipe.

[0082] The Venturi-boosted overflow assembly calculates a throat negative pressure of 19 kPa using the Venturi throat negative pressure equation when the main drainage riser flow velocity is 1.2 m / s. This negative pressure suction automatically draws sewage into the backup drainage pipe through the throat overflow branch pipe interface, with the suction flow accounting for 28% of the main pipe flow, achieving automatic diversion without power. The overflow pipe inner diameter is designed to be 80 mm, with a filling degree controlled at 0.65, allowing for ample air circulation space.

[0083] An automatic air regulating valve, a two-way pressure regulating device, is installed at the top of the throat of the Venturi-charged overflow assembly. When the overflow pipe drains rapidly and the pressure inside drops to -2.5 kPa, the automatic air regulating valve activates its intake mode to prevent air from forming a lock and obstructing water flow. When the pressure inside the overflow pipe rises to +1.2 kPa, the automatic air regulating valve activates its exhaust mode to prevent excessive air accumulation in the pipe from affecting flow capacity. A vacuum breaker is installed at the end of the overflow pipe, 0.4 meters from the inlet of the backup drainage pipe, with a negative pressure threshold set to -2 kPa. When the overflow pipe finishes draining and a negative pressure forms inside, creating a siphon effect, the vacuum breaker automatically introduces air to break the siphon, preventing excessive water level drop in the main drainage riser due to continuous suction.

[0084] like Figure 6 As shown, in the residential building renovation plan using a dual-pipe drainage system for bathrooms, the overflow pipe is discharged to an inspection well, which remains a separate discharge point on the first floor. Furthermore, the overflow pipe is combined with the vent pipe to form a dual-pipe system. Compared to... Figure 5 The single riser system shown is Figure 6 The ventilation risers in the building are connected to the atmosphere at the top and to the main drainage riser at the bottom, forming a dual-riser ventilation system. The technical team installed ventilation riser connection points every six floors along the main drainage riser, with each riser having an inner diameter of 55mm. This dual-riser ventilation system balances the pressure difference between floors in the main drainage riser through airflow, preventing pressure surges on lower-floor drainage branch pipes when the pressure at the bottom of the main drainage riser in high-rise buildings reaches 95kPa. The lower-floor drainage branch pipes are designed to withstand a pressure of 25kPa. The backflow risk caused by pressure differences is effectively eliminated through the pressure balancing effect of the ventilation risers. Alarm valves and overflow alarm devices are installed at key monitoring locations in the system, enabling timely warnings and activation of the overflow diversion mechanism.

[0085] A water-sealed anti-backflow valve assembly was installed at the connection between the drainage branch pipes on the first floor and in the basement and the main drainage riser. This assembly includes a valve body, a water seal chamber, and a spring-loaded pressure valve disc. The water seal chamber depth is set to 50mm. During normal drainage, the water flow opens the spring-loaded pressure valve disc. When backflow occurs due to high-rise drainage pressure, the water seal chamber isolates the airflow, and the spring-loaded pressure valve disc is pressed shut under spring force, achieving a pressure resistance of 150kPa. This water-sealed anti-backflow valve assembly, in conjunction with a water trap installed on the drainage branch pipe, forms a double protection system. The water seal depth of the water trap is 70mm.

[0086] The backup drainage pipe is connected to the municipal backup drainage well, which is 5 meters deep. The water level difference between the main drainage riser and the municipal backup drainage well serves as the overflow driving force. The technical team also configured a temporary storage device with a volume designed to be 1.8 times the design flow rate of the main drainage riser per hour, ensuring sufficient buffer capacity when the municipal backup drainage well is temporarily unable to discharge in a timely manner.

[0087] A flow meter is installed at a height of 0.4 meters from the bottom of the main drainage riser to measure the instantaneous flow rate in real time. The flow velocity in the main drainage riser is obtained by dividing the instantaneous flow rate by the cross-sectional area of ​​the main drainage riser. This flow velocity data is input into the Venturi throat negative pressure equation to calculate the throat negative pressure value, realizing the automatic matching function between the suction flow rate and the flow velocity in the main drainage riser. The higher the flow velocity in the main drainage riser, the greater the suction flow rate, ensuring effective diversion under different water use conditions.

[0088] The technical team conducted multiple operational tests on the modified drainage system, and the test data are shown in Table 1.

[0089] Table 1 System operating parameters under different operating conditions

[0090]

[0091] As shown in Table 1, the system can automatically adjust the pumping flow rate ratio according to different operating conditions. During heavy rain, the pumping flow rate ratio reaches 28%, while during normal water use, the ratio is only 18%, achieving automatic flow matching. The overflow initiation prediction time is within the range of 0.6 to 1.8 minutes, ensuring that the overflow mechanism is activated in advance before the water level reaches the danger level.

[0092] The technological advancements of this invention compared to traditional drainage systems are mainly reflected in the following aspects. First, the Venturi-intensified overflow assembly utilizes the Venturi effect to achieve automatic diversion without power. As sewage flows through the contraction section, the increased flow velocity leads to a decrease in pressure at the throat. Under negative pressure suction, the sewage is automatically drawn into the backup drainage pipe, eliminating the need for an additional power drive device and reducing system complexity and energy consumption. Second, the dual-probe ultrasonic level monitoring assembly calculates the rate of water level rise based on the difference in water levels between the upper and lower probes. This allows for early prediction of peak water levels and triggering of the overflow initiation signal, offering higher prediction accuracy and response speed compared to traditional single-point level monitoring methods. Third, the combined use of an automatic air regulating valve and a vacuum breaker effectively solves the problems of airlock and siphoning during overflow pipe drainage, ensuring that the overflow pipe's flow capacity is unaffected by air accumulation and negative pressure. Fourth, the dual-riser ventilation system balances the pressure difference between floors in the main drainage riser through airflow, eliminating the pressure shock caused by the pressure at the bottom of the main drainage riser in high-rise buildings on the drainage branch pipes of lower floors. This fundamentally solves the risk of backflow caused by pressure imbalance in traditional single-riser systems. Fifth, the water-sealed anti-backflow valve assembly, together with the water trap, forms a double protection, which can reliably isolate airflow and withstand high pressure when backflow occurs in high-rise drainage pressure. Compared with traditional single anti-backflow measures, it has higher safety and reliability.

[0093] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preventing sewage backflow in residential building sewers using overflow pipes, characterized in that, An overflow interface is installed at a height of 0.8 to 1.2 meters from the bottom of the main drainage riser, and a Venturi booster overflow assembly is installed. A dual-probe ultrasonic level monitoring assembly is installed at a height of 1.5 to 2 meters from the bottom of the main drainage riser. The water level rise rate is calculated based on the water level data collected by the dual-probe ultrasonic level monitoring assembly using a set of water level rise rate calculation equations. The water level rise rate determines whether the water level rise is rapid or slow and opens the overflow channel of the Venturi booster overflow assembly. An automatic air regulating valve is installed at the top of the throat of the Venturi booster overflow assembly. A vacuum breaker is installed at the end of the overflow pipe. A venting riser connection point is set every 5 to 8 floors along the main drainage riser. A water-sealed anti-backflow valve assembly is installed at the connection between the drainage branch pipes on the first floor and the basement and the main drainage riser.

2. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 1, characterized in that, The inlet diameter of the constriction section of the Venturi booster overflow assembly is the same as the inner diameter of the main drainage riser, the throat diameter is 0.6 to 0.7 times the inlet diameter of the constriction section, and the throat length is 2 to 3 times the throat diameter.

3. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 2, characterized in that, The upper probe of the dual-probe ultrasonic liquid level monitoring component is installed 80 to 120 mm above the warning water level line, and the lower probe is installed at the warning water level line. The vertical distance between the upper and lower probes is 80 to 120 mm.

4. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 3, characterized in that, When the water level rise rate is greater than 15 mm / min, it is determined to be a rapid water level rise condition; when the water level rise rate is less than or equal to 15 mm / min, it is determined to be a slow water level rise condition.

5. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 4, characterized in that, The overflow channel is opened when the water level is determined to be rising rapidly and the lower probe detects that the water level has reached the warning level. The overflow channel is opened when the water level is determined to be rising slowly and the upper probe detects that the water level exceeds the warning level by 60 to 80 mm.

6. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 5, characterized in that, When the internal pressure of the overflow pipe is lower than -2 kPa, the automatic air regulating valve opens the intake mode; when the internal pressure of the overflow pipe is higher than +1 kPa, the automatic air regulating valve opens the exhaust mode.

7. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 6, characterized in that, The vacuum breaker is installed at the end of the overflow pipe, 0.3 to 0.5 meters away from the inlet of the backup drainage pipe, and the activation negative pressure threshold is -1.5 to -3 kPa.

8. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 7, characterized in that, The top of the vent riser is connected to the atmosphere, and the bottom is connected to the main drainage riser. The inner diameter of the vent riser is 0.3 to 0.4 times that of the main drainage riser.

9. The method for preventing sewage backflow in residential building sewers using overflow pipes as described in claim 8, characterized in that, The equation set for calculating the rate of water level rise includes the equation for the rate of water level rise, the equation for the overflow initiation prediction time, and the equation for the negative pressure at the Venturi throat.

10. The method for preventing sewage backflow in residential building sewers using overflow pipes according to claim 9, characterized in that, The equation for the rate of water level rise is expressed as follows: the ratio of the rate of water level rise to 15 mm / min is equal to the ratio of the difference between the water level data from the upper probe and the water level data from the lower probe, divided by the quotient of the vertical distance between the upper and lower probes, divided by 0.15.

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