System and method for preventing backflow in multi-lateral branch vertical stormwater drains

Abstract

A branch pipe device for branching from a vertical pipe, the branch pipe device comprising: a branch joint mounted to the vertical pipe, a vertical portion forming a nozzle having a restricted cross section, the nozzle being arranged to increase the velocity head of water passing through the nozzle, an expansion chamber located directly below the nozzle, the expansion chamber having a cross sectional area greater than that of the vertical pipe; a branch portion protruding from the expansion chamber; a floor outlet; a branch pipe connecting the branch portion to the floor outlet.

Description

TECHNICAL FIELD

[0001] The present invention relates to rainwater discharge for wind-driven rainwater spaces. In particular, the invention relates to downpipes and associated branch pipes, such as those used for multi-storey buildings. BACKGROUND

[0002] Rainwater pipes with multiple levels of lateral branch connections have the risk of backflow of water through the lateral branches. This risk is difficult to predict with current gravity rainwater downpipe design principles.

[0003] The key factors that cause backflow in lateral branches are:

[0004] • release of air trapped within the piping system;

[0005] • unpredictability of two-phase flow behaviour when flow rates exceed a safe limit at which a clear separation between air and water can be maintained.

[0006] To prevent the above uncertainty, the flow rate of a vertically stacked stack must be limited to very low flow rates. Rainwater drainage codes in many countries have adopted the principle of not allowing lateral branch connections to vertical roof drainage pipes to prevent backflow problems.

[0007] At very low flow rates where the water flow does not affect the air flow, there is no risk of backflow. However, as the flow rate increases, the filling rate of water in the pipe increases. This increased water flow has an effect on the air inside the vertical pipe. The increased downward water flow can suck in additional air from the top of the vertical pipe, which is located at the roof, or from lateral branches located higher in the stack.

[0008] When the air brought along with the water flow can travel freely downward and freely discharge at the downstream end, for example a pipe that drains vertically into an open space, there is no risk of backflow.

[0009] However, in cases where the air cannot freely discharge at the downstream end of the pipe, for example:

[0010] • a long horizontal extension of the pipe downstream,

[0011] • the presence of a bend pipe at said downstream,

[0012] • confluence of fluid from other stacks, or

[0013] • a pipe discharge submerged due to overflow from an external drain, the air will escape through the multiple lateral branch connections, especially at the lower part of the stack.

[0014] The air escaping through the lateral branches creates 3 problems:

[0015] • prevent effective flow of water into the floor outlet which forms the entrance to the lateral branch;

[0016] • prevent effective flow of water through the lateral branch pipe;

[0017] • push water flowing in a vertical stack through the lateral branch, creating a backflow. SUMMARY

[0018] In a first aspect, the present invention provides a branch pipe arrangement for branching from a vertical pipe, the branch pipe arrangement comprising: a branch junction mounted to the vertical pipe, the vertical portion forming a nozzle having a restricted cross section, the nozzle being arranged to increase the velocity head of water passing through the nozzle, an expansion chamber located directly below the nozzle, the expansion chamber having a cross sectional area greater than the cross sectional area of the vertical pipe; a branch portion protruding from the expansion chamber; a floor outlet; a branch pipe connecting the branch portion to the floor outlet.

[0019] In a second aspect, the present invention provides a floor outlet for receiving a flow of water, the floor outlet comprising: a tap for connecting to a pipe; an inlet having two apertures, a first aperture for receiving an inflow of water and a second aperture for expelling air, the apertures being in fluid communication with the tap.

[0020] In a third aspect, the present invention provides an elbow pipe for providing an angled connection between two pipes, the elbow pipe comprising: an inner radius and an outer radius; wherein the inner diameter is large relative to the pipe diameter.

[0021] In a fourth aspect, the present invention provides an air release device for mounting to a pipe, the device comprising: a housing defining an internally vertical chamber; an opening in the base of the chamber for receiving air from the pipe; an air outlet at the top of the chamber for expelling the received air; wherein the height of the chamber is equal to or greater than the width of the chamber. BRIEF DESCRIPTION OF DRAWINGS

[0022] It will be convenient to further describe the present invention with reference to the accompanying drawings, which illustrate possible arrangements of the present invention. Other arrangements of the present invention are possible, and consequently, the particularity of the drawings should not be construed as a limitation on the generality of the preceding description of the present invention.

[0023] Figure 1 is an elevation view of a vertical pipe with a branch under stage 2 flow conditions;

[0024] Figure 2 is an elevation view of a vertical pipe with a branch under stage 3 and 4 flow conditions;

[0025] Figure 3 is a schematic elevation view of a vertical pipe and lateral branch;

[0026] Figure 4A is an isometric view of a bend according to an embodiment of the application;

[0027] Figure 4B is an isometric view of a bend according to an embodiment of the application;

[0028] Figure 4C is an isometric view of a flow outlet according to an embodiment of the application;

[0029] Figure 4D is an air release device according to an embodiment of the application;

[0030] Figure 5 is a schematic elevation view of a vertical pipe with a joint according to an embodiment of the application;

[0031] Figure 6 is a schematic elevation view of a joint according to an embodiment of the application;

[0032] Figures 7A to 7C is a schematic elevation view of a bend subjected to backflow conditions according to the prior art;

[0033] Figure 8 is a schematic elevation view of a bend according to an embodiment of the application;

[0034] Figure 9A and 9B is a schematic elevation view of a flow outlet according to an embodiment of the application;

[0035] Figure 10A and 10B are schematic elevation views of air release devices according to two embodiments of the application;

[0036] Figures 11A to 11D is a perspective view of various arrangements of vertical pipes and lateral branch pipes according to several embodiments of the application. DETAILED DESCRIPTION

[0037] Flow along a vertical pipe passes through the following stages (as flow increases)

[0038] • Stage 1 : very low flow rate, in which air and water are clearly separated. Water usually flows along the inner surface of the pipe wall and can be described as annular flow.

[0039] • Stage 2: low flow rate, in which the water flow affects the air flow in the pipe system. This flow stage causes additional air to be brought into the pipe system and causes air to accumulate at the lower part of the pipe.

[0040] • Phase 3: Two-phase flow phase: Flow rates where air and water mix together in the flow, with pressure fluctuations within the pipework. Flow conditions can be very unstable and unpredictable.

[0041] • Phase 4: Flow rates reach steady pressure flow conditions where the pressure is relatively stable. This is characterised by the presence of small air bubbles mixed with the water flow.

[0042] • Phase 5: Highest possible flow rate in a vertical stack when the flow rate reaches full bore flow conditions.

[0043] The risk of backflow occurs in phases 2, 3, 4 and 5. Conventional gravity design principles limit the capacity of gravity systems to flow rates in phase 1 in order to prevent any backflow.

[0044] Figure 1 shows a downpipe arrangement 5 with a vertical pipe 10 with a side branch 15. In phase 2, air 30 is brought down with the water flow. The problem arises when the increase in air pressure 20 forces air 35 to be pushed out sideways through the side branch. The escaping air intersects with the water flowing down the inside surface of the pipe wall and thus pushes water 25 into the side branch.

[0045] This causes water to accumulate in the side branch and eventually prevents air from escaping freely through the branch pipe. When this happens, air will push water upstream along the branch pipe and cause backflow.

[0046] Figure 2 shows the same arrangement 5 as figure 1 but with an increased water flow, progressing through phases 3 and 4 to phase 5. In this phase, the water flow has the characteristics of a pressure flow, with the downward water flow including entrained air, representing a two-phase flow. Since the flow through the branch connection has a higher pressure than atmospheric pressure, the water pressure will cause water 45 to be pushed out through the branch connection, resulting in backflow.

[0047] Air flow conditions within the side branch differ based on different flow conditions within the vertical stack. There are different air flow phases associated with the increase in flow rate through the vertical pipe:

[0048] • Phase 1: Minimal outward air flow against the direction of the water flow

[0049] • Phase 2: Maximum outward air flow against the direction of the water flow

[0050] • Phase 3: Minimal outward air flow against the direction of the water flow (similar to phase 1)

[0051] • Phase 4: Intermediate state with minimal air movement

[0052] • Phase 5: Inward air movement with the direction of the water flow

[0053] Critical conditions occur in stage 2 flow in branch pipes, which happens in stage 2 and stage 3 flow in vertical pipes. The solution to backflow needs to cater for the situation where there is a maximum outward air flow against the direction of water flow in the branch pipe.

[0054] Figure 3 Those locations in a vertical rainwater discharge pipe 50 with multiple layers of side branch connections that present a risk of backflow are shown, which are:

[0055] • Along the vertical stack 55 due to:

[0056] • Escape air pushing water out of the stack through the side branch;

[0057] • Pressure fluctuations within the vertical section of the pipe.

[0058] • At the connection point 60 between the vertical stack and the side branch;

[0059] • Along the side branch pipe 65 where the flow direction changes from horizontal to vertical, and;

[0060] • At the entry point 70 where water enters the side branch, such as a balcony floor outlet.

[0061] The invention relates to several aspects, each of which can be combined to address the problems identified in Figure 3 The various aspects can be used individually as required, but can also be used in combination with any or all of the other aspects to form a full system solution, if such a solution is required for a particular application.

[0062] Figures 4A to 4D Embodiments of the different aspects are shown arranged to address the situation at different locations:

[0063] • Figure 4A : Anti-backflow fitting 75 at the connection point where each side branch enters the vertical pipe

[0064] • Figure 4B : Adapted elbow 80 at each angle turn between vertical and horizontal in the branch pipe

[0065] • Figure 4C : Adapted floor outlet 85 where water enters the branch pipe

[0066] • Figure 4D : Adapted air release device 90, which can be incorporated into the anti-backflow fitting as well as other locations in the branch pipe.

[0067] Figure 5 A vertical pipe is shown with branches extending therefrom. Each branch includes an anti-backflow fitting 75.

[0068] As Figure 6 shown, the anti-backflow fitting 75 includes a restricted cross-section 120 which forms a nozzle level 124 with the opening 132 of the branch 134. This restriction creates an accumulation of water 100, 105 above the fitting 75, thereby creating a pressure head. This forces the flow pattern to switch from a gravity non-pressure flow to a pressure flow, the nozzle converts the pressure head into a high velocity head in the form of a high velocity jet 130 of water through the branch, and thus creates an air-water separation zone 125 through which trapped air can escape 135 vertically or horizontally through the branch 134. At high flow velocities in vertical pipes, the pressure jet achieves very high velocities which create a suction effect at the point of connection with the lateral branch. This increases the flow capacity of the lateral branch.

[0069] The wider separation zone 125 open to atmospheric pressure through the branch 134 also allows the water jet to expand, and thus return to a gravity directed flow.

[0070] At each point of connection, the nozzle causes a pressure disruption below the nozzle, while causing a pressure flow regime above the nozzle. This occurs at each branch point, regardless of the position of the fitting in the vertical pipe system and the height of the pipe system. Thus, the flow conditions in the vertical stack are divided into small, controlled pressure flow segments. Pressure fluctuations in the vertical stack are eliminated.

[0071] This enables the system to work under controlled pressure flow conditions, and enables much higher flow velocities to be achieved compared to conventional solutions which are only safe at stage 1 (very low flow velocity conditions).

[0072] In order for air to be able to escape through the lateral branch pipe without interfering with the water flow, a controlled water level in the lateral branch pipe is critical. The water flow needs to be designed to maintain an open channel condition at the horizontal section of the branch pipe.

[0073] While conventional gravity drainage pipe designs for horizontal pipes allow a water depth of up to 70% of the total depth of the pipe cross-section, this fill rate does not allow sufficient space for air to escape freely.

[0074] The maximum water depth at which air can escape freely through the branch pipe is 50% of the total depth of the pipe cross-section.

[0075] At water depths above 50% depth, a special air release device 90 can be incorporated into the anti-backflow fitting, as will be described with reference to Figures 11A to 11D .

[0076] Figures 7A to 7C Another point of vulnerability within the branch pipe arrangement due to backflow is shown. In the case where the water flow changes direction from the horizontal section of the branch pipe down to the vertical section of the pipe, the configuration of the elbow / bend 140 at the change of direction is critical to prevent backflow.

[0077] When the air flow 145 from the vertical section of the pipe intersects the water flow 150, due to the profile of the turn between the horizontal upstream section and the vertical downstream section, there is a risk of backflow that can be injected through the air flow path. In fact, this acts as a discontinuity for the water flow 150, causing it to separate from the pipe at this point 152. The upward air flow 145 will push 147, 160 the water back 155 and create an accumulation of water upstream of the turn and eventually a water plug 166 that can be pushed upstream for a long distance, causing backflow.

[0078] The turn with a sharp inner edge 152 (typical sharp 90-degree plastic fitting) tends to overshoot the water from the inside of the pipe wall, causing the injection of the flow beyond the center of the vertical section of the pipe.

[0079] Figure 8 A solution to this problem is shown with an adapted elbow 170. Having a curved surface, the elbow has an inner diameter 172 on the upper part of the elbow that helps to keep the water flow 190 along the lower part of the horizontal pipe by providing a continuous surface and thus preventing the separation between the water flow and the pipe. The water 195 follows the turn along the curved inside of the pipe wall. This prevents the intersection between the water flow and the air flow 175, 180, 185 and allows the change of direction of the flow to separate the air flow from the water flow.

[0080] According to the invention, an elbow 170 with a minimum inner diameter is used, which corresponds to twice the internal turn radius of 0.3 times the diameter of the pipe, to ensure that the water flow with a maximum depth of 50% does not intersect the air flow.

[0081] The enlarged part 178 at the outer radius of the elbow provides additional air space to avoid the interference of the air flow with the water flow. To this end, the cross-sectional area of the elbow defined by the line 171 connecting the centers 173, 174 of the inner and outer diameters is greater than the cross-sectional area of the upstream and downstream parts of the elbow including the sleeve of the elbow connected to the pipe.

[0082] In another embodiment, the radius of the inner part 172 of the elbow can be greater than the outer radius 176 of the elbow. Typically, elbows of the prior art have equal radii, or possibly an inner diameter smaller than the outer diameter. In another embodiment of the invention, the inner radius can be made larger to prevent separation when the water flows around the curve, and the outer radius can be made smaller, thus creating additional space for the air flow and keeping it separated from the water flow. Thus, the outer radius can approach zero due to the shape mimicking a rectangular corner.

[0083] In another aspect, Figures 9A to 9C A floor outlet 200 is shown that serves as an entry point for the water into the side branch. It is also the exit point for the air to escape from the side branch.

[0084] The conflict between the outgoing air and the incoming water can prevent effective discharge, in which case the water is prevented from entering the outlet and subsequently the branch pipe.

[0085] In this embodiment, the floor outlet 200 has a horizontal tap 208 which ensures that air travels in the upper part of the pipework and enters a chamber 240 which has a larger cross-sectional area than the tap and thus expands relative to the tap, said chamber having an upper and lower part. Note that while a horizontal tap is shown in the figures, the tap can be vertical. In another alternative, depending on the Figure 8 The elbow is connected to or integral with the sleeve. At the other end of the outlet 200, in fluid communication with the sleeve is an inlet having two apertures 214, 215. The first aperture 215 is arranged to receive the inflow of water, the second aperture 214 is arranged to discharge air from the pipework. Air at the upper part of the pipe cross-section is directed towards the centre of the floor outlet, at the centre of the floor outlet the air is allowed to escape 230 through the second aperture 214 without interfering with the inflow of water 220 through the first aperture 215. The inlet of the second aperture is defined by an inner edge 213 which in turn is connected to a canopy 210. The first aperture is defined by a peripheral edge 205 and the inner edge 213. When the floor outlet is positioned, the peripheral and inner edges are arranged to be flush with the surface of the floor, although a conventional ramp directs water to the inlet. Thus the water flow 220 received by the outlet 200 is directed through the first aperture 215 and is directed into the lower part 235 of the chamber 240, the water flow 225 is then allowed to flow into the horizontal pipe 208.

[0086] The floor outlet 200 has 2 main features:

[0087] • A vertical expanding air chamber 240 at the junction between the branch pipe 208 and the floor outlet 205. This expanding part 240 allows additional upward air space in the upper part to direct the air flow towards the air vent opening at the centre.

[0088] • A semi-circular canopy 210 extending from the wall of the floor outlet towards the centre directs the air flow to be released in the centre of the outlet. This allows the air flow to be released outwards from the floor outlet to be separated from the water flow which flows inwards into the floor outlet.

[0089] Figure 10AAn air release component 245 is shown. The air release component 245 is arranged to be used in the vicinity of a branch to facilitate the release of trapped air and thus help overcome backflow issues at the branch. It will thus be in fluid communication with the branch and vertically above said branch, but not necessarily directly above. While it can be installed in isolation from other aspects of the invention, when used in conjunction with an anti-backflow fitting, for example, the air release component allows for immediate direct release of air at the connection point of the fitting, thereby reducing / eliminating the need to release air through the branch pipe. This can allow the branch pipe to be in full bore condition, i.e. 100% underwater discharge, which significantly increases its discharge capacity. The chamber within the housing can have a height equal to or greater than the width of the chamber. Its cross-sectional area can also be greater than that of the branch or branch pipe.

[0090] The air release device 245 comprises a housing 250 with a top 255. In the base of the device is an opening 265 which fits to a sleeve or other fitting on or near the tap. The opening 265 allows air to escape from the branch pipe. The air enters a chamber 285 and passes through a central tray 270 which in this case is an inverted conical plate. The tray 270 comprises a central vent hole 273 and peripheral vent holes 271, 275 around the perimeter of the tray 270. The conical shape of the tray allows a ball 277 to sit within the device 245 when not activated. When air enters the chamber 285 and passes 280 into the tray 270, the air eventually exits through an air outlet 260 in the top of the device 255 and thus out of the device.

[0091] A floating ball 277 is incorporated in the device to ensure that in the event that water is introduced into the device, the device will self-seal against the air outlet 260, with the ball 279 rising and falling based on the water level within the device.

[0092] Figure 10B An alternative arrangement is shown in which one or more baffles 274 are attached to the device top 255 and arranged to move 276 from an open position to a closed position, sealing the top air outlet 260 and sealing the top air outlet as water flows in from the base.

[0093] It will be appreciated that the ball functions in a similar way to a one-way valve, and it will thus be appreciated that the ball can be replaced by a freely moving disc which floats on top of the rising water level to seal the air outlet;

[0094] As mentioned above, the invention comprises four different aspects, as listed in Figures 4A to 4D While these components can be used in isolation, they can be used together to form a branch pipe arrangement.

[0095] For example, Figures 11A to 11DVarious combinations are shown that can be used for such branch pipe arrangements, which are intended to provide a continuous air path and a continuous inflow path, both separated from each other to prevent air from being trapped in the branch pipe.

[0096] Figure 11A : High fill rate with vertical drop in branch pipe

[0097] • Branch arrangement 295 with branch junction 305 having air release device 310, two elbows 315, and floor outlet 320;

[0098] Figure 11B : Low fill rate with vertical drop in branch pipe

[0099] • Branch arrangement 325 with branch junction 305, two elbows 315, and floor outlet 320;

[0100] Figure 11C : High fill rate with branch pipe directly accessing anti-backflow junction

[0101] • Branch arrangement 330 with branch junction 305 having air release device 310 and floor outlet;

[0102] Figure 11D : Low fill rate with branch pipe directly accessing anti-backflow junction

[0103] • Branch arrangement 335 with branch junction 305 and floor outlet 320;

[0104] Each branch pipe arrangement includes various components to achieve high flow rates using pressure flow principles while effectively preventing backflow at the side branch.

Claims

1. A floor outlet for receiving a flow of water, the floor outlet comprising a faucet for connecting to a pipe; and an inlet having an open first aperture for receiving an inflow of water and an open second aperture for discharging air, the open apertures being in fluid communication with the faucet, wherein the open second aperture being defined by an inner edge; and wherein the open first aperture is defined by a peripheral edge and the inner edge such that the open second aperture is positioned within the open first aperture.

2. The floor outlet of claim 1, further comprising a chamber intermediate the faucet and the apertures, the chamber having a cross-sectional area greater than the faucet.

3. The floor outlet of claim 2, wherein the chamber comprises an upper section and a lower section, the upper section being arranged to receive air from the pipe and discharge air to the second aperture, the lower section being arranged to receive the inflow from the first aperture and direct the inflow to the pipe.

4. The floor outlet of any one of claims 1 to 3, wherein the peripheral edge is flush with a floor into which the floor outlet has been placed.

5. The floor outlet of claim 3, wherein the chamber comprises a cover, the cover covering the upper section of the chamber, wherein the cover forms a first conduit for flowing air from the faucet located below a front section of the inlet to the second aperture; and the cover forms a second conduit for flowing water from a front section of the inlet to a rear section of the inlet, thereby directing water flow to the faucet through the rear section of the inlet.

6. An elbow for providing an angled connection between two pipes, the elbow comprising an inner radius and an outer radius; wherein the inner radius is greater than a pipe diameter.

7. The elbow of claim 6, wherein the outer radius is less than a pipe diameter.

8. The elbow of claim 6, wherein the outer radius is less than the inner radius.

9. The elbow of claim 6, wherein twice the inner radius is greater than or equal to 0.3 times the pipe diameter.

10. The elbow of claim 6, wherein a cross-sectional area of the elbow along a line connecting centers of the inner and outer radii is greater than a cross-sectional area of a pipe to which the elbow is connected.

11. An air release device for mounting to a pipe, the device comprising: a housing defining an interior chamber oriented vertically; an opening in a base of the chamber for receiving air from the pipe; an air exhaust at a top of the chamber for discharging the received air to an ambient environment; wherein a height of the chamber is equal to or greater than a width of the chamber; and wherein the received air is communicated from the base of the chamber through the height of the chamber to the air exhaust at the top of the chamber.

12. The air release device of claim 11, further comprising a tray within the chamber, the tray horizontally spanning the chamber; wherein the tray comprises an air exhaust arranged to allow the received air to pass through the tray.

13. The air release device of claim 12, further comprising a ball in the chamber and above the tray, the ball being configured to float on a flow of water from the base and to seal the vent.

14. The air release device of claim 11, further comprising at least one baffle adjacent to the top of the chamber, the baffle being configured to move from an open position to a closed position to seal the vent when water flows in from the base, and to seal the vent.

15. A branch pipe device for branching from a vertical pipe, the branch pipe device comprising: A branch connector is installed to the vertical pipe, the vertical pipe having a limited cross-section in its vertical portion to form a nozzle, the nozzle being arranged to increase the velocity of water passing through the nozzle; An expansion chamber located directly below the nozzle, the cross-sectional area of ​​which is larger than the cross-sectional area of ​​the vertical tube; A branch protruding from the expansion chamber; Floor outlet according to any one of claims 1 to 6; as well as The branch is connected to the branch pipe of the floor outlet.

16. The branch pipe device of claim 15, further comprising an air release device according to any one of claims 11 to 14, the air release device being mounted close to and in fluid communication with the branch.

17. The branch pipe device according to claim 15 or 16, wherein the branch pipe includes a first bend adjacent to the branch portion to guide the pipe horizontally.

18. The branch pipe device of claim 17, wherein the branch pipe includes two additional bends between the first bend and the floor outlet.

19. The branch pipe device of claim 18, wherein, At least one of the first bend and the additional bend is a bend according to claims 6 to 10.

20. A method for separating an air path and an inflow path in a branch pipe, the method comprising the steps of: The flow in the branch pipe is diverted and compressed to create a nozzle within the branch pipe. This induces a pressure flow upstream of the nozzle and generates a water jet downstream of the nozzle, and thus; An air separation zone is formed at the opening of the branch pipe; The inflow material is received in the first hole at the outlet at the opposite end of the branch pipe, and air is discharged from the second hole at the outlet, and thus; A continuous air path is formed from the air separation zone to the second hole, and a continuous inflow path is formed from the first hole to the branch pipe.

21. The method of claim 20, further comprising the step of: Redirect air from the air path in the branch pipe to the air release device; Air is discharged from the air release device.

22. The method of claim 20 or 21, further comprising the step of guiding the inflow path between the first hole and the branch pipe along a continuous curved surface in the bend of the branch pipe.

23. The method of claim 22, further comprising the step of directing air to an enlarged portion adjacent to the curved surface.

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