GB2547259A - Improved syphon - Google Patents

Abstract

The syphon 100 comprises a pumping chamber 10 having a primary inlet 12 for water and a secondary inlet 14 for air, and a passage having an inlet 22 in fluid communication with the secondary inlet and defining a flow cut-off point, wherein when water enters the primary inlet and passes through the chamber during a syphoning event the continuous flow of water is stopped by air coming into the chamber through the passage inlet, and wherein the passage inlet is movable such that the flow cut-off point is movable between the primary and secondary inlets. The passage may be variable in length, and comprise a channel 30 around the secondary inlet and an adjuster 40 slidably moveable about the channel, wherein an open end of the channel is the passage inlet. The adjuster may have arms that slidably engage with inner edges of the channel. Also claimed are a pumping chamber and adjuster for use with the syphon.

Description

Improved Syphon

FIELD

[01] The disclosure relates to an improved syphon, particularly, although not exclusively to syphons for cisterns.

BACKGROUND

[02] Syphons having devices for adjusting the flush volume of a cistern are known. For example, dual-flush syphons allow a partial (i.e. short) flush and a full (i.e. long) flush to be achieved from the same syphon. Activation of either the partial flush or the full flush is achieved through movement of the diaphragm, which is normally coupled to a lever or button.

[03] In addition, solutions to vary the extent of the full flush are known. Typically, these solutions include a plurality of predetermined holes formed in a bell housing (i.e. the pumping chamber) of a syphon, wherein all but one of the holes are closed using at least one plug. The unplugged hole is then used to encourage air into the bell housing during the continuous flow of water through the syphon in a syphoning event (i.e. syphonic action) in order to break the natural flow of water. Each of the plurality of holes is arranged at a different level on the bell housing so that different full flush volumes can be achieved depending on which hole is left unplugged.

[04] Conventional full flush adjustment solutions are inconvenient because the proper fitment and repositioning of plugs can be awkward and any loose plugs can easily be dropped into the cistern or lost entirely. Furthermore, good access to the side of the bell housing is required for practical accuracy (i.e. in order to see the hole in which the plug will be manually inserted into). The side access also requires close visual inspection to ascertain the current full flush adjustment setting (i.e. which hole is unplugged), which can be awkward and inaccurate. Sometimes, the complete removal of the syphon from the cistern is required to make an adjustment, which is inconvenient. In addition, finely tuned full flush adjustment is not possible with conventional systems because of the discrete increments. Finally, the manufacture of holes and plugs requires further manufacturing steps and the use of different materials.

[05] It is therefore desirable to provide a syphon with an improved adjustable “full” flush device. A more convenient solution is advantageous to avoid or reduce the risk of improper setup or loss of components. A device that can be more easily adjusted (i.e. practically/manually and/or visually) and/or that has a larger range of settings is desired. A further aim is to provide a system that is more durable, robust or simple. Ultimately, the aim is to provide a better full flush system that is more user friendly so that the disadvantages and drawbacks associated with conventional syphons can be overcome.

SUMMARY

[06] According to the present invention there is provided a syphon as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

[07] According to the disclosure, a syphon for a cistern is provided. The syphon comprises a pumping chamber having a body with a hole provided in the side of the body. The body has an open base for receiving flushing water to be syphoned to a water closet (WC) pan. The hole is provided above the base of the syphon and is fluidly communicable with an adjuster. The adjuster has an inlet that is moveable with respect to the hole so that the point at which air enters the syphon is variable. Thus, the point at which syphonic action can be broken in use is also variable. Preferably, the adjuster inlet is infinitely variable between the open base and the hole in order to provide fine adjustment of the full flush volume. More preferably, the adjuster is slidably moveable relative to the hole and/or is vertically moveable along the exterior side walls of the bell housing. Advantageously, a full flush volume can be varied using the adjuster and can be finely tuned for a given scenario. Furthermore, only a single hole is required in the side of the body of the pumping chamber, for achieving a full range of full flush adjustment settings thus simplifying complexity of manufacture and installation variety. This helps to reduce the problems of leakage between component parts due to poor fitment and therefore improper sealing.

[08] According to an exemplary embodiment, a syphon fora cistern is provided. The syphon comprises a pumping chamber (known as a bell housing) having a primary inlet for a first fluid (i.e. a liquid, such as water) and a secondary inlet for a second fluid (i.e. a gas, such as air). The inlets are configured such that the second fluid for introduction through the secondary inlet is a relatively less dense fluid compared to the first fluid. Preferably, the first fluid is water for flushing a water closet (WC) pan, the water arranged to be contained within the cistern and surround the syphon. The second fluid is preferably ambient air that can be drawn in from above the level of the water provided in a cistern. The syphon comprises a passage (i.e. a passageway or tunnel) having an open end which is an inlet that is in fluid communication with the secondary inlet of the pumping chamber. The passage inlet is used to define a flow cut-off point for breaking the flow of the first fluid during a syphoning event (i.e. syphonic action).

During a syphoning event, i.e. when the first fluid continuously enters the primary inlet and passes through the pumping chamber, the continuous flow of the first fluid can be stopped by the introduction of the second fluid into the pumping chamber by passing the second fluid through the passage inlet. This is arranged to occur when the passage inlet ceases to be submerged in the first fluid at the flow cut-off point. Prior to this, the passage inlet is fully submerged in the first fluid until the level of the first fluid in the cistern decreases to the passage inlet. Beneficially, the passage inlet is arranged to be moveable relative to the secondary inlet of the pumping chamber. Since the passage inlet determines the location of the flow cut-off point, the flow cut-off point is thus moveable between the primary and secondary inlets.

[09] Advantageously, the solution of this disclosure, particularly the moveable passage inlet, provides greater convenience and flexibility to a user and/or installer. This avoids the need to remove plugs from holes as is currently known with adjustable full flush syphons. Consequently, the risk of the loss of parts or the risk of poor/fiddly fitment of component parts is reduced or removed entirely. This gives an installer or general user of the device greater confidence.

[10] Preferably, the passage comprises passage walls that fluidly link the passage inlet with the secondary inlet. That is, the passage walls fluidly couple the passage inlet and secondary inlet in order to direct (i.e. route) the second fluid from the passage inlet to the secondary inlet. Preferably, the passage walls are continuous so that the only exit points are the passage inlet and secondary inlet. This is because the second fluid should only enter through the passage inlet and not at another point when the passage inlet at least partially covers the secondary inlet. Advantageously, a well define routing device is provided that provides a repeatable air pathway for the second fluid to reach the secondary inlet.

[11] The passage may be arranged such that the second fluid enters the passage inlet first and then proceeds to enter the secondary inlet during a flow cut-off event. That is, the second fluid enters the inlet of the passage before passing along the passage and finally entering the secondary inlet of the pumping chamber. Preferably, the passage is formed on the exterior of the pumping chamber (i.e. over the exterior surfaces of the pumping chamber). This utilises the pumping chamber for a further purpose other than simply housing a pumping mechanism, such as a diaphragm. This also allows the passage to be manipulated without the interfereing with any internal components of the pumping chamber, such as a diaphragm. The passage may be therefore provided on a side of the pumping chamber. The passage may be variable in length, i.e. the passage may not have a fixed length. The length of the passage may be directly proportional to the distance between the secondary inlet and the flow cut-off point. Advantageously, the route that the second fluid has to take to reach the secondary inlet is minimised. This avoids the risk of damage to the passage, particularly when the passage is tubular, i.e. a pipe or tube, that may have a fixed length.

[12] The syphon may comprise a channel (i.e. a slot) provided at least partly around the secondary inlet for routing the second fluid to the secondary inlet and for receiving an adjuster. Said adjuster may be slidably moveable about the channel. The adjuster governs the position of the passage inlet because the adjuster and channel define an open end within the channel that corresponds to the passage inlet. As the adjuster moves about the channel, the extent of an opening of the channel between channel walls may vary. The adjuster is therefore provided as a cover that at least partially covers the secondary inlet. When the adjuster does not cover the secondary inlet, the passage inlet and secondary inlet are substantially one and the same because the passage is minimised or no longer has an effect on the air pathway. The adjuster is a sliding member that slides relative to the secondary inlets. The direction of the sliding movement may be towards and away from the primary inlet and may be in a linear direction between the primary and secondary inlets. Advantageously, the sliding movement is user friendly because it is easy to use and avoids the risk of improper alignment and fitment. The sliding action is repeatable and time efficient. Furthermore, when orientated correctly, the adjuster provides the advantage that the adjustment can be more easily made from above the syphon. Therefore, accurate positioning and re-positioning of the adjuster is possible whilst installed within the cistern. By removing the need to access the sides of the syphon in order to adjust the full flush volume, the improved syphon can be fitted into narrow cisterns because the need for maintenance access is reduced. This is because the adjuster can be moved by sliding movement in a direction parallel to the side of the bell housing rather than in a direction outwardly from the side (i.e. in a generally radial direction of a diaphragm plate movement). Beneficially, this provides more operational flexibility and is more convenient for a user and/or installer.

[13] The walls of the passage may comprise the inner surfaces of the adjuster and/or the inner surfaces of the channel. The channel may extend all the way to the primary inlet. The adjuster may also be capable of moving all the way to the primary inlet. The channel may be formed on the exterior of the pumping chamber. The adjuster may cover the side walls of the channel such that when the adjuster is in contact with the channel, the channel is hidden from view when viewing the syphon in a side direction. Alternatively, the channel may be integral to the syphon body (e.g. pumping chamber) or alternatively made from separate components and coupled to the syphon.

[14] The adjuster may have outwardly extending arms provided on the lateral extents (i.e. sides) of the adjuster. The arms may slidably engage with inwardly facing edges of the channel such that the adjuster is moveable within the channel rather than moveable over the channel. Furthermore, the adjuster may be an elongate member such that the adjuster moves in a linear fashion.

[15] The adjuster may be temporarily held in place by resistance, i.e. friction, or may be temporarily fixed by a series of protrusions and grooves that interact to removably hold the adjuster in position at discrete intervals. Beneficially, the adjuster can be moved along a sliding scale. Additionally, or alternatively, a locking member may be provided to hold the adjuster in place. The locking member may be used to restrain the adjuster so that the passage inlet is unable to move relative to the pumping chamber. Advantageously, the positive engagement of the locking member or the protrusions and grooves provides improved positional control of the adjuster. Given sufficient resistance forces, this may also occur with friction working against the movement of the adjuster.

[16] The channel may comprise a sealing member to control the routing of the second fluid towards the secondary inlet. Alternatively, a face seal may be provided that provides face to face seal between parts, i.e. the channel and the adjuster. Therefore, the adjuster and/or channel may be provided a face seal. At least one sealing member may be provided on the adjuster and move with the adjuster relative to the secondary inlet. For example, an open loop sealing member (i.e. a sealing member having essentially two ends) may be used to define a single open end of the channel in the region of the passage inlet. The sealing member therefore enables fluid communication through the passageway in a predetermined way. Preferably, the channel that is engageable with the adjuster comprises a plurality of sealing members. Each sealing member may be coupled to the channel rather than to the adjuster in order to resist movement of the adjuster and provide a good seal for the passage. Preferably, the resistance of movement is tactile. The coupling may be permanent or temporary to allow replacement. Preferably, the channel is substantially vertical when the syphon is arranged in a cistern so that the adjuster is vertically moveable. Preferably, the adjuster is provided with a gripping portion so that the adjuster can be easily gripped when wet. The gripping portion is preferably provided at a distal extent of the adjuster that is the furthest away from the primary inlet when arranged in the channel.

[17] Preferably, the passage inlet has an infinite number of locations (i.e. adjustment settings or positions) between two extremes (i.e. the primary and secondary inlets) rather than a discrete number of positions. The flow cut-off point may therefore be infinitely variable between the primary and secondary inlets. Advantageously, a syphon with greater flexibility is provided.

[18] The syphon may comprise a third inlet, i.e. a tertiary inlet that is used for providing a partial flush. Therefore, when the primary and secondary inlets are used to define a full flush, the tertiary inlet provides the partial flush. That is, the partial flush is arranged to allow less volume of the first fluid (i.e. water) through the syphon as compared to the volume of the first fluid through the syphon with a full flush. The tertiary inlet may be provided in or on the pumping chamber. Furthermore, the secondary and tertiary inlets may be provided further away from the primary inlet in that order when measured in the same direction from the primary inlet. That is, the tertiary inlet may be arranged to be provided further away from the primary inlet than the secondary inlet when measured in substantially the same direction.

[19] According to a further embodiment, a pumping chamber for a syphon as previously described is provided. Preferably, the pumping chamber is arranged to be releasably coupled to an overflow tube (i.e. a u-shaped pipe that is inverted when coupled to the pumping chamber).

[20] According to yet another embodiment, an adjuster for a syphon as previously described is provided.

[21] Advantageously an improved adjustable “full” flush system is provided. The disclosure herein avoids or reduces the risk of improper set-up of the adjustment device or the complete loss of individual components. The device can be more easily and accurately adjusted and/or offers a larger range of settings to the user and/or installer. More accurate settings provide the potential for water saving benefits and reduced environmental impact. Overall, a better syphon and a better adjustable full flush system is provided.

BRIEF DESCRIPTION OF DRAWINGS

[22] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: [23] Figure 1 shows a side view of an improved syphon with a full flush adjuster; [24] Figure 2a shows a cross-sectional view through the syphon of Figure 1 showing the spatial arrangement of the full flush adjuster; [25] Figure 2b shows a cross-sectional view through line X-X of Figure 1 of an alternative embodiment of Figure 2a.

[26] Figure 3 shows the syphon of Figure 1 with the full flush adjuster removed; and [27] Figure 4 shows the syphon of Figure 1 whereby the full flush adjuster is in a raised position in order to effect a cut-off of the full flush.

DESCRIPTION OF EMBODIMENTS

[28] Figure 1 shows a side view of an improved syphon 100 for fitment within a cistern (not shown). The syphon 100 comprises a housing 10, which is commonly known as a bell housing. The housing 10 works as a pumping chamber (both terms are used interchangeably herein) because the housing 10 is arranged to comprise a movable pumping member such as a diaphragm. The pumping member is used to establish a syphoning event (i.e. syphonic action) that causes the continuous flow of water through the syphon and into a WC pan. The pumping member may be moveable by an actuating means. The actuating means may be an actuating stem, rod or button, any of which may be electronically controllable.

[29] The pumping chamber 10 is a hollow component that has an open end at the base of the housing 10. This opening or hole is the main or primary inlet 12 for receiving the flushing water from the cistern. Although not shown, the primary inlet 12 is specifically sized to provide the smallest opening possible whilst allowing the pumping mechanism to operate effectively.

[30] The pumping chamber 10 is further provided with a secondary inlet 14 (shown in dashed lines) that allows air to infiltrate into the syphon 100 in order to halt the syphoning event. The secondary inlet 14 is positioned on the side of the syphon 100 at a location higher than the base of the pumping chamber 10. Therefore, when positioned in a cistern, the secondary inlet 14 is arranged to be positioned at a higher location than the primary inlet 12, closer to the surface of the water when the cistern is full with water to be flushed to a WC pan.

[31] An adjustment member or adjuster 40 is configured over the secondary inlet 14 as shown in Figure 1. This adjuster 40 is sealably engaged with a channel 30 (see Figures 2a and 2b) such that air is drawn between the adjuster 40 and the channel 30 beneath the adjuster 40 on its way to the secondary inlet 14. As shown in Figure 1b, a passageway 20 is created between the adjuster 40 and channel 30 that fluidly communicates with the secondary inlet 14. The passage or passageway 20 is essentially an air path for directing air into the syphon 100 to break the syphoning event. The passage 20 has an inlet 22 that allows air to enter the passage 20 and reach the secondary inlet 14 by channelling air towards the secondary inlet 14. Although the passage inlet 22 is shown to be coexistent with the primary inlet 12 in Figure 1, the passage inlet 22 may be moved away from the primary inlet 12, i.e. towards the secondary inlet 14 (see Figure 3). This is because the adjuster 40 is slidably moveable about the channel 30. The movement of the adjuster 40 governs the position of the passage inlet 22. As shown in Figure 1, the adjuster 40 and channel 30 are also elongate such that linear movement of the adjuster 40 about the channel 30 can be easily achieved.

[32] When the passage inlet 22 is provided away from the primary inlet 12, the break in the flow of water during a syphoning event occurs sooner than that caused by the primary inlet 12. This is because the passage inlet 22 is arranged to be provided further away from the base of the cistern when the syphon 100 is fitted to a cistern than the primary inlet 12.

[33] Movement of the adjuster 40 can be discrete or can be smooth such that the adjuster is infinitely varied between the primary 12 and secondary 14 inlets. In any event, visual markings 44 to indicate the position of the adjuster 40 can be provided on the adjuster 40 itself. These visual markings 44 may be tactile so that the current position can be easily felt by the hands of a user avoiding the need to visually inspect the position. Therefore, the markings 44 may be tactiovisual markings that are both tactile and visual. Furthermore, the adjuster 40 may be provided with a gripping portion 46 at the distal tip (i.e. distal extent) of the adjuster 40 in order to improve the ability to grip the adjuster 40, which is particularly useful when the adjuster 40 is wet.

[34] The interaction between the adjuster 40 and channel 30 is shown by the cross-sectional view of the adjuster 40 and channel 30 combination in Figure 2a. Here, a face-to-face seal is provided between the adjuster sides 42 and the channel side walls 32 so that fluid is unable to pass between the face-to-face sliding contact. Such a face seal provides a fluid-tight seal that prevents air from entering or leaving the channel. This is advantageous because the air that will eventually break the syphonic action can only enter though the passage inlet 22. The face-to-face contact preferably removes the need for a further sealing member, such as a viscoelastic member. Although not shown, the passage 20 comprises a rear wall so that air is directed to the passage inlet 20. The passage 20 is generally u-shaped and orientated in the same direction as the inverted u-shaped tube (the overflow tube) that is configured to be coupled to the pumping chamber 10. The removal of the need for an additional sealing member simplifies the arrangement.

[35] Alternatively, the adjuster 40 and channel 30 may be fluid tight through the use of a sealing member. Such an arrangement is shown in Figure 2b, using the cross-section through X-X. Here, the passageway 20 is shown beneath the adjuster 40 and arranged between internal side walls 32 of the channel. The walls 24 of the passageway 20 are also shown. The cross-section omits the wall thickness of the pumping chamber 10 across the passageway 20 and the seal within the passageway 20 in order to more clearly show the extent of the passageway 20. Of course, some form of seal (i.e. a sealing member 50 bridging the internal side walls 32 of the channel 30) would be required in order to ensure that the passage 20 is properly sealed and that the only opening to the passage 20 is the passage inlet 22. As shown in Figure 2b, sealing members 50 are provided along the inner walls 32 of the channel 30 and are engageable with lateral arms 42 of the adjuster 40. The sealing members 50 may be fitted to the channel 30 and may by removable therefrom in order to replace the sealing members 50 when damaged or worn. The adjuster 40 has outwardly protruding arms 42 that are arranged to abut and form a moveable seal with the sealing members 50. The arms 42 run along the side walls 32 of the channel 30 and are at least partly contained by the side walls 32. Alternatively, sealing members 50 may not be required as long as the passage inlet 22 is the only way in which the air can enter the passage 20 and pass into the syphon 100 in order to cut-off syphonic action. For example, surface seals formed between the channel and the adjuster (i.e. a face-to-face seal) avoid the need for a separate sealing member, as described in relation to Figure 2a.

[36] The adjuster 40 and channel 30 engage to form an adjustable full flush mechanism. However, the syphon 100 may be further provided with a tertiary inlet 60 that is used to achieve a partial flush. The tertiary inlet 60 is provided at a higher location than the secondary inlet 14. The secondary inlet 14 is further provided at a higher location than the primary inlet 12. Therefore, the variation of the passage inlet 22 is configured to directly vary the full flush volumes, whereas the tertiary inlet 60 is directed to partial flush volumes.

[37] Figure 2 shows the channel 30 of the pumping chamber 10 more clearly. A groove 52 is provided at the top of the channel 30 that is capable of receiving a sealing member 50, wherein the sealing member 50 is used to prevent fluid entering the passage 20. The groove 52 is located above the secondary inlet 14.

[38] As further shown in Figure 3, the syphon 100 has been adjusted for producing a reduced full flush volume (compared to that generated by the primary inlet 12). This has been achieved by moving the adjuster 40 in direction Y by holding onto the gripping portion 46 and pulling the adjuster 40. This direction is shown as a vertical direction. The adjuster 40 is then held in position at the higher end of location “6” by, for example, friction resisting movement of the adjuster 40. The adjuster is defined at location “6” because the top of the channel 30 is most closely aligned with the lines defining the upper limit of the “6” range, as shown on the visual indicator 44. At this location, the passage inlet 22 is arranged away from the base of the pumping chamber 10 where the primary inlet 12 resides. This determines a new cut-off point. When the level of the water in the cistern drops to an air inlet, the syphoning event stops. Therefore, when the passage inlet 22 is arranged further away from the base of the syphon 100, the cut-off point is determined by the passage inlet 22. When the level of the water coincides with the passage inlet 22, air is drawn by the movement of water through the pumping chamber 10 along the passage 20 and into the pumping chamber 10 via the secondary inlet 14. This results in a disruption in the fluid flow and the syphoning event comes to a halt. In the event that a short flush (i.e. a partial flush), the user will activate the syphon 100 such that air is caused to enter the higher tertiary inlet 60 and break the syphoning event before air can enter either the secondary 14 or primary 12 inlets.

[39] Advantageously, an improved syphon 100 is provided. The moveable passage inlet 22 of the syphon 100 allows greater fine tuning of the full flush volume in order to provide greater end use and flexibility and potential for water saving benefits and reduced environmental impact. The adjuster 40 helps to provide more a convenient adjustment solution which avoids the need to access the side wall of the pumping chamber 10. Furthermore, the risk of loss of component parts is reduced or avoided as is the risk of poor fitment of parts. Overall, a better syphon 100 is provided that solves the drawbacks associated with conventional syphons.

[40] Although preferred embodiment(s) of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made without departing from the scope of the invention as defined in the claims.

Claims (21)

1. A syphon for a cistern, the syphon comprising: a pumping chamber having a primary inlet for a first fluid and a secondary inlet for a second relatively less dense fluid; and a passage having an inlet in fluid communication with the secondary inlet of the pumping chamber, the passage inlet defining a flow cut-off point; wherein when the first fluid continuously enters the primary inlet and passes through the pumping chamber during a syphoning event the continuous flow of the first fluid is stopped by the introduction of the second fluid into the pumping chamber through the passage inlet when the passage inlet ceases to be submerged in the first fluid at the flow cut-off point; wherein the passage inlet is moveable with respect to the secondary inlet such that the flow cut-off point is moveable between the primary and secondary inlets.

2. The syphon according to claim 1, wherein the passage comprises walls fluidly coupling the passage inlet and secondary inlet in order to direct the second fluid from the passage inlet to the secondary inlet.

3. The syphon according to any preceding claim, wherein the passage is arranged such that the second fluid first enters the passage inlet and then the secondary inlet during a flow cut-off event.

4. The syphon according to claim 3, wherein the passage is formed on the exterior of the pumping chamber.

5. The syphon according to any preceding claim, wherein the passage is variable in length.

6. The syphon according to any preceding claim, wherein the length of the passage is directly proportional to the distance between the secondary inlet and the flow cut-off point.

7. The syphon according to any one of claims 3 to 6, wherein the syphon comprises a channel provided at least partly around the secondary inlet and an adjuster slidably moveable about the channel, wherein the channel has an open end corresponding to the passage inlet.

8. The syphon according to claim 7, wherein the channel extends all the way to the primary inlet.

9. The syphon according to claim 7 or 8, wherein the channel is formed on the exterior of the pumping chamber.

10. The syphon according to claim 9, wherein the adjuster has outwardly extending arms provided on the lateral extents of the adjuster that slidably engage with inner edges of the channel such that the adjuster is moveable within the channel.

11. The syphon according to any one of claims 7 to 10, wherein the channel comprises a sealing member.

12. The syphon according to any one of claims 7 to 10, wherein the channel comprises an open loop sealing member such that the open end is provided in the region of the passage inlet.

13. The syphon according to any one of claims 7 to 10, wherein the channel comprises a plurality of sealing members.

14. The syphon according to claim 12 or 13, wherein each sealing member is coupled to the channel and resists movement of the adjuster.

15. The syphon according to any one of claims 7 to 14, wherein the channel is substantially vertical when the syphon is arranged in a cistern so that the adjuster is vertically moveable.

16. The syphon according to any preceding claim, wherein the flow cut-off point is infinitely variable between the primary and secondary inlets.

17. The syphon according to any preceding claim, wherein the syphon comprises a tertiary inlet that defines a partial flush and the primary and secondary inlets define a full flush, wherein the partial flush is arranged to allow less volume of the first fluid through the syphon than the full flush.

18. The syphon according to claim 17, wherein the tertiary inlet is provided in the pumping chamber.

19. The syphon according to claim 17 or 18, wherein the secondary and tertiary inlets are provided sequentially further away from the primary inlet when measured in the same direction from the primary inlet.

20. A pumping chamber for a syphon according to any preceding claim.

21. An adjuster for a syphon according to any one of claims 7 to 19.