Backflow preventer and lifting system
Patent Information
- Application Number
- PCT/EP2025/055491
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-05
- Filing Date
- 2025-02-28
- Publication Date
- 2025-10-02
AI Technical Summary
Existing backflow preventers for wastewater systems are prone to contamination, require frequent maintenance, and lack redundancy, leading to potential pump failure and safety issues, especially in continuous operation scenarios.
A dual-pump backflow preventer design with two independent check valves and a housing that allows for inspection and maintenance access, ensuring continuous operation and redundancy by enabling two pumps to operate alternately, with each check valve having its own inspection opening and fastening mechanism.
The dual-pump system enhances safety and reliability by allowing one pump to operate continuously even if the other fails, preventing flooding and ensuring uninterrupted wastewater transport.
Smart Images
Figure EP2025055491_02102025_PF_FP_ABST
Abstract
Description
[0001] Backflow preventer and lifting station
[0002] Description
[0003] The invention relates to a backflow preventer for a lifting station and / or pumping station or a lifting station with a pumping station, in particular a backflow prevention device for wastewater systems, as well as a lifting station for lifting a liquid.
[0004] A sewage lifting station lifts wastewater from buildings or other structures located below the sewer system level and pumps it into the sewer system. This is particularly necessary in areas with unfavorable terrain or in building basements where the wastewater cannot drain sufficiently due to natural conditions. The sewage lifting station collects the wastewater and pumps it into higher-lying sewer pipes or channels, where it can then drain naturally. The system typically consists of a pump, a collection tank, a backflow assembly, and various control and safety devices to ensure reliable operation.
[0005] A backflow preventer assembly is known from DE 76 31 732 U1. This discloses a check valve for installation in a pipeline with a housing forming a pipe section. The housing has an opening for inserting the check valve. This opening allows access to the check valve and is closed during operation with a threaded plug.
[0006] This design has the disadvantage that the thread of the threaded plug can become contaminated and is difficult to open. At the same time, this housing design only allows for the connection of one pump, meaning the load is always on that one pump. With increased performance, this can lead to increased wear on the pump due to the increased demands on the backflow preventer. If only one pump can be connected, continuous operation cannot be ensured, meaning safety cannot be guaranteed in the event of a pump failure.
[0007] The object of the present invention is to provide a backflow prevention device for wastewater systems and a lifting system for lifting a liquid, which enables continuous operation, so that safety is increased and protection against flooding or damage caused by wastewater can be guaranteed.
[0008] This object is achieved by a backflow preventer for a water lifting system according to claim 1 and a lifting system for lifting a liquid according to claim 11.
[0009] A first aspect of the invention is a backflow preventer for a lifting station or pumping station or a lifting station with a pumping station with
[0010] - a housing, wherein the housing
[0011] - forms a first liquid channel, a second liquid channel and a liquid collection channel, wherein the first liquid channel and the second liquid channel merge into the liquid collection channel, wherein the liquid collection channel has a central axis, and
[0012] - has at least one inspection opening, and with
[0013] - a first non-return valve, wherein the first non-return valve is arranged in the first fluid channel of the housing, so that the first non-return valve can be inspected via the at least one inspection opening and
[0014] - a second check valve, wherein the second check valve is arranged in the second fluid channel of the housing, wherein the second check valve is inspectable via the at least one inspection opening, and
[0015] - at least one inspection cover, wherein the at least one inspection cover closes the at least one inspection opening in a fluid-tight manner.
[0016] The backflow preventer can also be referred to as a double-pump backflow preventer or backflow prevention device, since a pump can be connected to both the first fluid channel and the second fluid channel. A lifting station, for example, is understood here as a water lifting station. It is advantageous if the housing has a first pressure connection for connecting a first pump to the first fluid channel and a second pressure connection for connecting a second pump to the second fluid channel, as well as a pipe connection for connecting a pressure line to the fluid collection channel.
[0017] The housing can be made of a plastic, such as polyurethane, using an injection molding process. It's also conceivable for the housing to be made of metal, although cast iron has proven particularly advantageous. Regardless of the material, a casting process is suitable for manufacturing due to the shape of the backflow preventer.
[0018] The first check valve is then arranged in the first fluid channel between the first pressure connection and the pipe connection. Similarly, the second check valve is arranged in the second fluid channel between the second pressure connection and the pipe connection.
[0019] The first and second check valves are designed in such a way that they can be brought into an open position by a flow from the respective pressure connection to the pipe connection.
[0020] When the pump(s) are not in operation, it is advantageous if the first and second check valves are closed. The liquid column in the lifting station's discharge line, which can be connected or flanged to the pipe connection of the liquid collection channel of the backflow preventer, prevents the first and second check valves from opening accidentally. This prevents unwanted backflow of liquid into the collection tank even when the pumps are switched off, thus increasing the safety of the lifting station or pumping station.
[0021] If only one pump is in operation in the lifting unit or pumping station, the check valve assigned to this pump remains open. Whereas the check valve assigned to the pump that is not in operation remains closed to prevent pumping into the collecting tank. The two check valves can be one-piece or multi-piece. In a multi-piece design, the check valves can have a check valve body and, depending on the application, a weight on the check valve body or something similar. It is conceivable that in a multi-piece check valve all individual components are made of the same or different materials. The use of an elastomer, particularly polyurethane, has proven particularly advantageous for the one-piece check valve or check valve body.
[0022] The advantage of the dual-pump check valve is that the use of two pumps significantly increases the reliability of the system. Should one pump fail or require maintenance, the other pump can continue to operate. This has a positive impact on operations, as the redundancy ensures continuity of pumping. The use of two pumps thus increases the safety of the system.
[0023] This backflow preventer is designed so that the first and second check valves are accessible, i.e., replaceable and cleanable, via a common access opening. Therefore, the access cover only needs to seal the access opening fluid-tight. This reduces both the number of components and the costs.
[0024] It is particularly advantageous if the first check valve is inspectable via the at least one inspection opening and the at least one inspection cover closes the at least one inspection opening in a fluid-tight manner and that the second check valve is inspectable via a second inspection opening and a second inspection cover closes the second inspection opening in a fluid-tight manner.
[0025] In this embodiment, each check valve is assigned its own inspection opening with its own inspection cover. This allows each check valve to be individually inspected and, if necessary, replaced. This increases design flexibility and safety. Furthermore, it is advantageous for the backflow preventer if the first fluid channel is arranged at a first angle of 10° to 70°, preferably 20° to 50°, more preferably 30° to 45°, to the central axis of the fluid collection channel. Additionally or alternatively, the second fluid channel can be arranged at a second angle of 10° to 70°, preferably 20° to 50°, more preferably 30° to 45°, to a central axis of the fluid collection channel.
[0026] Particularly even load distribution during pumping, especially when the pumps are operated alternately, can be achieved if the angle and the second angle are identical.
[0027] The angles of the fluid channels to the fluid collection channel create a Y-shaped flow channel. At the transition from the first and second fluid channels to the fluid collection channel, the first and second angles can positively influence the flow conditions in the fluid collection channel and further along the discharge line. At the same time, adjusting the angles can accommodate design specifications or structural limitations.
[0028] Furthermore, it is conceivable that a first center point of the first fluid channel and a second center point of the second fluid channel are arranged on an imaginary circle around the center axis of the fluid collection channel. An arc length between the first center point and the second center point corresponds to 5% to 50%, preferably 10% to 45%, more preferably 15% to 40%, of the circumference of the imaginary circle.
[0029] The imaginary circle is arranged on a sectional plane through the housing orthogonal to the central axis of the liquid collection channel.
[0030] Furthermore, in this context, the arc length is understood as the length of the arc as a segment of the circumference. Accordingly, the corresponding arc length is explicitly dependent on the distance between the center of the circle on the central axis of the fluid collection channel and the first center or the second center, i.e., the radius of the circle, as well as the angle of the sector spanning between the center of the circle and the first center of the first fluid channel and the second center of the second fluid channel.
[0031] This allows for a wide variation in the design and thus in the size of the backflow preventer without having to forego the advantages of redundancy by means of the two pumps or the two independently functioning fluid channels.
[0032] Furthermore, it is advantageous for the backflow preventer if the first check valve has a first fastening section for fastening to the housing, and the second check valve has a second fastening section for fastening to the housing. The first fastening section can be connected to the housing by means of a screw connection, a rivet connection, a press connection, or a clip connection. Alternatively or additionally, the second fastening section can be connected to the housing by means of a screw connection, a rivet connection, a press connection, or a clip connection.
[0033] This ensures that the function of the first or second check valve is not affected by the type of mounting, or that the mounting is not negatively affected by the flapping of the check valve. Furthermore, the mounting section enables easy and quick disassembly and assembly of the check valves.
[0034] A multi-part check valve is particularly advantageous in this case. This allows the design and adaptation of the mounting section in terms of both size and shape, as well as the choice of material, depending on the fluid, the pump pressure, or the size of the fluid channel.
[0035] In a further embodiment of the backflow preventer, it can be advantageous if the housing has a first fastening area in the first fluid channel for fastening, in particular the first fastening section, the first check valve and a second fastening area in the second fluid channel for fastening, in particular the second fastening section, the second check valve. The first fastening area can be connectable to, in particular the first fastening section, the first check valve by means of a screw connection or a rivet connection or a press connection or a clip connection. Additionally or alternatively, the second fastening area can be connectable to, in particular the second fastening section, the second check valve by means of a screw connection or a rivet connection or a press connection or a clip connection.
[0036] This ensures the safety and functionality of the check valves in their respective fluid channels. At the same time, a predefined mounting area allows for easy disassembly and secure reassembly of the check valves.
[0037] It is particularly advantageous if both a first fastening section on the first check valve and a first fastening area in the first fluid channel are provided. It is also advantageous if a second fastening section on the second check valve and a second fastening area in the second fluid channel are provided. This ensures a secure connection of the check valves and facilitates disassembly and assembly, as precise positioning of the check valves on the housing is achieved, especially during assembly.
[0038] It may be advantageous if the first fastening region of the first fluid channel and / or the second fastening region of the second fluid channel have a minimal distance from the central axis of the fluid collection channel. Additionally or alternatively, the first fastening region of the first fluid channel and / or the second fastening region of the second fluid channel can have a maximum distance from the central axis of the fluid collection channel.
[0039] The position of the mounting area allows the opening direction of the check valves to be selected for the course of the respective fluid channel. This allows the course of the fluid channels to be adapted to size specifications. The courses and arrangement of the first fluid channel and the second fluid channel can be different. The function of the check valve can be particularly advantageous if the first fluid channel and the second fluid channel are arranged mirror-symmetrically to the central axis of the fluid collection channel.
[0040] In a further embodiment of the backflow preventer, the at least one inspection cover is arranged at an angle of 20° to 80°, preferably 30° to 70°, more preferably between 40° and 60°, to the central axis of the fluid collection channel. If a second inspection cover is provided, it can also be advantageous for it to be arranged at an angle of 20° to 80°, preferably 30° to 70°, more preferably between 40° and 60°, to the central axis of the fluid collection channel. This requires that the inspection opening is also arranged at the same angle.
[0041] Furthermore, the access cover can be connected to the housing by means of a screw connection or a clip connection to ensure a fluid-tight seal around the access opening. A seal can also be provided.
[0042] This allows for easy removal and installation of the inspection cover. At the same time, the angle allows for an increased cross-section of the inspection opening, making it easier to inspect the check valves.
[0043] In a further embodiment of the backflow preventer, it provides a ball valve in the housing, wherein the ball valve is designed to drain the liquid from the liquid collection channel. When the backflow preventer is installed in a lifting station or pumping station, the ball valve can be used to drain the liquid from a pressure line via the liquid collection channel.
[0044] The ability to drain the fluid using the ball valve is particularly advantageous for inspection or checking the functionality of the backflow preventer.
[0045] A second aspect of the invention is a lifting station or pumping station or a lifting station with a pumping station for lifting and moving a liquid, in particular a wastewater lifting station, with - a backflow preventer as described above according to the first aspect,
[0046] - a collecting container for collecting liquid, especially waste water,
[0047] - a pressure line, whereby the pressure line is connected to the liquid collecting channel of the non-return valve
[0048] - a first pump, wherein the first pump is connected to the first fluid channel of the non-return valve and
[0049] - a second pump, wherein the second pump is connected to the second fluid channel of the backflow preventer, wherein the first pump and the second pump are designed to pump the medium from the collecting container via the backflow preventer into the pressure line and into a further reservoir or a sewer channel.
[0050] The pressure line can be connected to the fluid collection channel via the housing's pipe connection. Furthermore, the first pump can be connected to the first fluid channel via the first pressure connection. Furthermore, the second pump can be connected to the second fluid channel via the second pressure connection.
[0051] Having two pumps significantly increases the reliability of the lifting station. Should one pump fail or require maintenance, the other pump can continue operating. In this case, the check valve of the failed pump remains closed, and the fluid is pumped via the operating pump and its associated check valve.
[0052] Alternating operation of the first and second pumps is also conceivable. The use of the pumps can be changed over time or as needed.
[0053] Additionally, the two pumps allow for higher flow rates. This is particularly advantageous in situations with increased wastewater volumes or in large buildings with extensive wastewater systems.
[0054] Even in the event of a pump failure, the second pump can continue operation, ensuring no interruption in wastewater transport. A dual-pump lifting station offers a higher level of safety by providing additional protection against potential failures or malfunctions, which is especially important for preventing flooding or damage caused by wastewater.
[0055] In another embodiment of the lifting station, the backflow preventer is arranged between the first pump and the second pump. It is also conceivable for the backflow preventer to be arranged parallel to the first pump and the second pump.
[0056] The arrangement of the first and second pumps can be selected depending on the available size. This increases flexibility in the design.
[0057] The invention is described below using an exemplary embodiment, which is explained in more detail with reference to the figures. Herein:
[0058] Figure 1 is a schematic view of the backflow preventer according to the invention in an isometric representation;
[0059] Figure 2 is a schematic view of a sectional view of the backflow preventer in a front view;
[0060] Figure 3 is a schematic view of the backflow preventer in a plan view;
[0061] Figure 4 is an isometric view of a check valve of the backflow preventer;
[0062] Figure 5 is a schematic view of a lifting system according to the invention.
[0063] The backflow preventer of Fig. 1 to 4 is equipped with a housing 12, a first check valve 22, a second check valve 24 and at least one inspection cover 26.
[0064] The housing 12 forms a first fluid channel 14, a second
[0065] The backflow preventer 10 comprises a first fluid channel 16 and a fluid collection channel 18, which are illustrated in the sectional view of Fig. 2. The first fluid channel 14 and the second fluid channel 16 merge into the fluid collection channel 18. The fluid collection channel 18 has a central axis MA and is essentially circular. In the exemplary embodiments according to Figs. 1 to 5, the housing 12 of the backflow preventer 10 has two inspection openings 20. In addition, a ball valve 36 is provided on the housing 12 to enable the fluid to be drained from the fluid collection channel 18.
[0066] In order to be designed for installation in a lifting system 50, as shown in Fig. 5, the housing 10 has a first pressure connection 15 for connecting a first pump 56 to the first liquid channel 14 and a second pressure connection 17 for connecting a second pump 58 to the second liquid channel 16, as well as a pipe connection 19 for connecting a pressure line 54 to the liquid collecting channel 18.
[0067] The first check valve 22 is arranged in the first fluid channel 14 of the housing 12, so that the first check valve 22 can be inspected via the at least one inspection opening 20. The second check valve 24 is arranged in the second fluid channel 16 of the housing 12, so that the second check valve 24 can be inspected via the at least one inspection opening 20. In order to ensure fluid-tightness during use of the backflow preventer 10, the at least one inspection cover 26 closes the at least one inspection opening 20 in a fluid-tight manner. For this purpose, a seal can be provided between the inspection cover 26 and the inspection opening 20.
[0068] 1 to 3, the first liquid channel 14 and the second liquid channel 16 are arranged mirror-symmetrically to the central axis MA of the liquid collection channel 18. The first liquid channel 14 is arranged at a first angle α of approximately 30° and from 10° to 70° to the central axis MA of the liquid collection channel 18. This therefore applies analogously to the second angle β between the second liquid channel 16 and the central axis MA of the liquid collection channel 18. To determine the first angle α and the second angle β, a virtual leg is taken from the first center point M1 and the second center point M2, respectively, to a center point M3 of the liquid collection channel 18 on the central axis. The first liquid channel 14 and the second liquid channel 16, together with the liquid collection channel 18, form the entire flow channel, which in this case has a Y-shape.
[0069] Therefore, in this case, two inspection openings 20 are provided. The first check valve 22 is accessible via one inspection opening 20, and an inspection cover 26 seals the at least one inspection opening 20 in a fluid-tight manner. The second check valve 24 is accessible via a second inspection opening 20, and a second inspection cover 26 seals the second inspection opening 20 in a fluid-tight manner.
[0070] The plan view according to Fig. 3 shows that a first center point M1 of the first fluid channel 14 and a second center point M2 of the second fluid channel 16 are arranged on an imaginary circle K around the center axis MA of the fluid collection channel 18. In the illustrated embodiment, the arc length BL corresponds to 50% of the circumference of the imaginary circle K.
[0071] In an embodiment not shown, the arc length BL can be 5% or 10% of the circumference of the imaginary circle K. In this case, it is conceivable that the two fluid channels 14, 16 are so close to each other that only one inspection opening 20 with an inspection cover 26 is necessary.
[0072] Fig. 4 shows a check valve, which in Fig. 2 is installed in the backflow preventer as both the first and second check valve. It can be seen that the first check valve 22 has a first fastening section 28 for fastening to the housing 12 and the second check valve 24 has a second fastening section 30 for fastening to the housing 12. In the illustrated embodiment, the first fastening section 28 and the second fastening section 30 can be connected to the housing 12 by means of a screw connection. The illustrated fastening section 28, 30 can be reinforced by a metal plate, which simplifies screwing in to establish the connection to the housing 12.
[0073] Since the first and second check valves are fastened to the housing 12 by means of a screw connection, the housing 12 has a first fastening area 32 in the first fluid channel 14 for fastening the first fastening section 28 of the first check valve 22 and a second fastening area 34 in the second fluid channel 16 for fastening the second fastening section 30 of the second check valve 24.
[0074] Due to the Y-shape and the associated flow direction, the opening direction of the first and second check valves 22, 24 is also predetermined. These must therefore be mounted in such a way that, when open, the flow path to the fluid collection channel 18 is clear. Accordingly, in the illustrated embodiment, the first mounting area 32 of the first fluid channel 14 and the second mounting area 34 of the second fluid channel 16 have a maximum distance A_max from the center axis MA of the fluid collection channel 18.
[0075] For a space-saving design and to enlarge the inspection openings for the first and second check valves 22, 24, the respectively assigned inspection covers 26 are each arranged at an angle y of approximately 50°, i.e. between 20° and 80° to the central axis MA of the liquid collection channel 18.
[0076] Fig. 5 shows a lifting system 50 for lifting a liquid, in particular a wastewater lifting system 50. This system comprises a backflow preventer 10 according to one of Figs. 1 to 4, a collecting tank 52 for collecting liquid, in particular wastewater, a pressure line 54, a first pump 56, and a second pump 58.
[0077] The pressure line 54 is connected to the fluid collection channel 18 of the backflow preventer 10 via the pipe connection 19. The first pump 56 is connected to the first fluid channel 14 of the backflow preventer 10 via the first pressure connection 15. The second pump 58 is connected to the second fluid channel 16 of the backflow preventer 10 via the second pressure connection 17. The first pump 56 and the second pump 58 are designed to pump the fluid from the collection container 52 via the backflow preventer 10 into the pressure line 54 and into another reservoir or a wastewater channel. The pumps 56, 58 are operated alternately, as can be seen from the position of the first reset flap 22 and the second reset flap 24 in Fig. 2.
[0078] Due to the structural design of the backflow preventer 10 described above and shown in Figs. 1 to 4, the backflow preventer 10 is arranged between the first pump 56 and the second pump 58.
[0079] Reference symbol
[0080] 10 backflow preventers
[0081] 12 housings
[0082] 14 first fluid channel
[0083] 15 first pressure connection
[0084] 16 second fluid channel
[0085] 17 second pressure connection
[0086] 18 Fluid collection channel
[0087] 19 Pipe connection
[0088] 20 Inspection opening
[0089] 22 first check valve
[0090] 24 second check valve
[0091] 26 Inspection cover
[0092] 28 first fortification section
[0093] 30 second fastening section
[0094] 32 first fastening area
[0095] 34 second fastening area
[0096] 36 ball valve
[0097] 50 lifting station
[0098] 52 collection containers
[0099] 54 pressure line
[0100] 56 first pump
[0101] 58 second pump
[0102] 0 first angle ß second angle Y angle
[0103] MA central axis
[0104] Ml first center
[0105] M2 second center point
[0106] M3 third center point
[0107] K imaginary circle
[0108] BL arc length
[0109] A_min minimum distance
[0110] A_max maximum distance
Claims
Claims 1. Non-return valve (10) for a lifting station (50) or pumping station or a lifting station (50) with a pumping station with - a housing (12), wherein the housing (12) - forms a first liquid channel (14), a second liquid channel (16) and a liquid collection channel (18), wherein the first liquid channel (14) and the second liquid channel (16) merge into the liquid collection channel (18), wherein the liquid collection channel (18) has a central axis (MA), and - has at least one inspection opening (20), and with - a first non-return valve (22), wherein the first non-return valve (22) is arranged in the first liquid channel (14) of the housing (12), so that the first non-return valve (22) can be inspected via the at least one inspection opening (20) and - a second check valve (24), wherein the second check valve (24) is arranged in the second fluid channel (16) of the housing (12) so that the second check valve (24) can be inspected via the at least one inspection opening (20), and - at least one inspection cover (26), wherein the at least one inspection cover (26) closes the at least one inspection opening (20) in a fluid-tight manner.
2. Backflow preventer (10) according to claim 1, characterized in that the first check valve (22) is inspectable via the at least one inspection opening (20) and that the at least one inspection cover (26) closes the at least one inspection opening (20) in a fluid-tight manner and that the second check valve (24) is inspectable via a second inspection opening (20) and a second inspection cover (26) closes the second inspection opening (20) in a fluid-tight manner.
3. Backflow preventer (10) according to claim 1 or 2, characterized in that the first liquid channel (14) is arranged at a first angle (α) of 10° to 70°, preferably 20° to 50°, more preferably 30° to 45°, to the central axis (MA) of the liquid collecting channel (18) and / or that the second liquid channel (16) is arranged at a second angle (β) of 10° to 70°, preferably 20° to 50°, more preferably 30° to 45°, to the central axis (MA) of the liquid collecting channel (18).
4. Backflow preventer (10) according to one of the preceding claims, characterized in that a first center point (Ml) of the first liquid channel (14) and a second center point (M2) of the second liquid channel (16) are arranged on an imaginary circle (K) around the center axis (MA) of the liquid collecting channel (18), wherein an arc length (BL) between the first center point (Ml) and the second center point (M2) corresponds to 5% to 50%, preferably 10% to 45%, more preferably 15% to 40%, of the circumference of the imaginary circle (K).
5. Backflow preventer (10) according to one of the preceding claims, characterized in that the first check valve (22) has a first fastening section (28) for fastening to the housing (12) and the second check valve (24) has a second fastening section (30) for fastening to the housing (12), wherein the first fastening section (28) and / or the second fastening section (30) can be connected to the housing (12) by means of a screw connection or a rivet connection or a press connection or a clip connection.
6. Backflow preventer (10) according to one of the preceding claims, characterized in that the housing (12) in the first liquid channel (14) has a first fastening area (32) for fastening, in particular the first fastening section (28), the first check valve (22) and in the second liquid channel (16) a second fastening area (34) for fastening, in particular the second fastening section (30), the second check valve (24), wherein the first fastening region (32) can be connected to, in particular the first fastening section (32), the first check valve (22) by means of a screw connection or a rivet connection or a press connection or a clip connection and / or the second fastening region (34) can be connected to, in particular the second fastening section (30), the second check valve (24) by means of a screw connection or a rivet connection or a press connection or a clip connection.
7. Backflow preventer (10) according to claim 6, characterized in that the first fastening region (32) of the first liquid channel (14) and / or the second fastening region (34) of the second liquid channel (16) has a minimum distance (A_min) from the central axis (MA) of the liquid collecting channel (18) and / or that the first fastening region (32) of the first liquid channel (14) and / or the second fastening region (34) of the second liquid channel (16) has a maximum distance (A_min) from the central axis (MA) of the liquid collecting channel (18).
8. Backflow preventer (10) according to one of the preceding claims, characterized in that the first liquid channel (14) and the second liquid channel (16) are arranged mirror-symmetrically to the central axis (MA) of the liquid collecting channel (18).
9. Backflow preventer (10) according to one of the preceding claims, characterized in that the at least one inspection cover (26), and in particular the second inspection cover (26), is arranged at an angle (y) of 20° to 80°, preferably 30° to 70°, more preferably between 40° and 60°, to the central axis (MA) of the liquid collecting channel (18).
10. Backflow preventer (10) according to one of the preceding claims, characterized in that a ball valve (36) is provided in the housing (12), wherein the Ball valve (36) is designed to drain the liquid from the liquid collection channel (18).
11. Lifting station (50) or pumping station or a lifting station (50) with a pumping station for lifting or moving a liquid, in particular a wastewater lifting station (50), with - a backflow preventer (10) according to one of the preceding claims, - a collecting container (52) for collecting liquid, in particular waste water, - a pressure line (54), wherein the pressure line (54) is connected to the liquid collecting channel (18) of the backflow preventer (10) - a first pump (56), wherein the first pump (56) is connected to the first liquid channel (14) of the backflow preventer (10) and - a second pump (58), wherein the second pump (58) is connected to the second liquid channel (16) of the backflow preventer (10), wherein the first pump (56) and the second pump (58) are designed to pump the liquid from the collecting container (52) via the backflow preventer (10) into the pressure line (54) and into a further reservoir or a sewer channel.
12. Lifting system (50) according to claim 11, characterized in that the backflow preventer (10) is arranged between the first pump (56) and the second pump (58) or that the backflow preventer (10) is arranged parallel to the first pump (56) and the second pump (58).