AU6858398A - Flush system - Google Patents

Description

FLUSH SYSTEM

Technical Field

The present invention relates to a flush system. In particular although not exclusively, the invention relates to a high pressure flushing cistern for sanitary apparatus where a charge of water is required to cleanse the apparatus periodically or between users. It will be appreciated that the invention will have application in toilets and urinals although the invention may be utilised in other apparatus requiring a discharge of water under pressure. A unique flush valve is also disclosed.

Background Art

Known pressure-assisted flush systems comprise a vessel which traps air and uses the water supply line pressure to compress the trapped air until the air and water pressure are equal at which time a main valve in the vessel may be opened with the compressed air forcing the water out of the vessel and typically into a toilet bowl. The advantages of such systems are twofold, a vigorous flushing action providing effective cleansing of the toilet bowl and such an effective cleansing action being achieved with less water.

Such systems can suffer from several disadvantages. The rush of pressurised water through the toilet vessel can create reduced pressure downstream of the bowl effectively removing all of the water from the toilet trap. In addition, the sudden exit of water from the flush vessel can also cause a sudden recoil of the push button. Moreover, difficulties in closing the flush valve are created by unpredictable movement of the valve member during operation. A number of solutions to these problems have been proposed which may or may not be effective in minimising the above problems. One thing that can be said about such systems is that they are generally complex assemblies requiring a myriad of parts including springs and diaphragms to perform effectively. It is therefore an object of the present invention to provide a flush system which overcomes or ameliorates at least some of the above mentioned disadvantages while achieving a degree of simplicity in design.

Disclosure of Invention

In accordance with a first aspect of the present invention there is provided a flush valve for a flush system, said flush valve including a chamber provided with one or more inlet ports and an outlet, a moveable valve member within the chamber moveable between an open position and a closed position blocking passage between the inlet port(s) and the outlet, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the valve member; and an actuation valve operable to drain fluid from said first portion of the chamber to reduce pressure in said portion and move the moveable valve member towards the open position, the actuation valve being operable by an actuation means extending from the outlet side of flush valve through the moveable valve member.

Preferably, where the moveable valve member is in the form of a cylindrical piston, the actuation means extends in substantial alignment with the central axis of the piston to the actuation valve which is disposed towards the first end of the piston.

Preferably, the actuation means is operable by a plunger member, the actuation means and the plunger member having mutually inclined engagement surfaces. The plunger member may be oriented substantially perpendicular to the longitudinal axis of the actuation means and moreover, in the whole flush system, the moveable valve member may be oriented for substantially horizontal movement thereby enabling the plunger member to extend in a substantially upright manner for a manual downward push movement in the conventional manner. Alternatively, an electronically controlled solenoid may be provided to control depression of the plunger and the duration of depression may thereby be controlled. This enables the user actuator to be remotely located from the flush system and the cistern. More importantly, this electronic control provides variable flush times and thus flush volumes only dependent on the overall cistern volume and water pressure.

In a most preferred form of the invention an opening or a bleed passage is provided in the chamber to expel liquid on the backward movement of the actuation valve towards the open position. Desirably, the opening remains open throughout the normal range of movement of the moveable valve member. A stop may be provided to ensure that the moveable valve member does not obstruct the opening. Alternatively a spring may be provided to bias the moveable valve member away from a position obstructing the opening.

In accordance with a second aspect of the present invention there is provided a flush system including: a pressure reducing valve for connection to a pressurised water supply, the pressure reducing valve adapted to reduce water pressure to a predetermined pressure; a closed cistern having a water inlet for continuous connection to the water supply downstream of the pressure reducing valve and a water outlet controlled by a flush valve, said flush valve including a chamber, a moveable valve member within the chamber moveable between a closed position and an open position, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the valve member; an actuation valve operable to drain fluid from said first portion of the chamber to reduce pressure in said portion to move said moveable valve member towards the open position; the chamber being further provided with one or more ports in communication with the cistern, a passage between the one or more ports and the water outlet being blocked by the moveable valve member in the closed position, the chamber being provided with a bleed passage between the cistern and said first portion of the chamber. Additionally, a non-return valve may be provided downstream of the pressure reducing valve.

The bleed passage between the cistern and the first portion of the chamber may be in the form of an opening provided in the chamber wall. Alternatively, the bleed passage may be simply exist between the sides of the movable valve member and the sides of the chamber.

Also described in the specification (but not claimed) is the invention of flush system including: a closed cistern having a water inlet for connection to a pressurised water supply and a water outlet controlled by a flush valve, said flush valve including a chamber, a moveable valve member within the chamber moveable between a closed position and an open position, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the valve member; an actuation valve located externally of the chamber to drain fluid from said first portion of said chamber to reduce pressure in said first portion and move the moveable valve member towards the open position, wherein the actuation valve is isolated from the cistern and the water supply when it is not operating to drain fluid from the first portion; the chamber being further provided with one or more ports in communication with the remainder of said cistern, a passage between the ports and the water outlet being blocked by the moveable valve member in the closed position.

The actuation valve may be located externally of the cistern. In one preferred form of the invention, the actuation valve may be remotely located whereby an actuator for the actuation valve is disposed at a convenient location for the user. Suitably, the actuation valve drains fluid from the first portion of the chamber to an outlet passage to beyond the cistern outlet. The actuation valve may be a simple on/off tap but is not limited to this type. Preferably, the actuation valve is a solenoid controlled valve which may be adjacent to the cistern with a remote actuator.

In a preferred form of the invention, an opening may be provided between the cistern and the first portion of the chamber. Suitably, this is in the form of a simple aperture or passage in the chamber wall disposed adjacent the first portion of the chamber. Preferably, where the flush valve is located above the cistern outlet with the first portion of the chamber being defined in an upper region of the chamber, the bleed hole is provided in the top chamber wall.

Also described in the specification (but not claimed) is another invention relating to a flush system including a closed cistern having a water inlet for connection to a pressurised water supply and a water outlet controlled by a flush valve, said flush valve including a chamber, a moveable valve member within the chamber moveable between a closed position and an open position, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the valve member; an actuation valve located externally of the chamber to drain fluid from said first portion to reduce pressure in said first portion and move the moveable valve member towards the open position; the chamber being further provided with one or more ports in communication with the cistern, a passage between each of the one or more ports and the water outlet being blocked by the moveable valve member in the closed position, the flush valve being such that flow of water through the passage will create a force acting directly on the moveable valve member, tending to push the moveable valve member towards the open position.

Preferably, the force of water alone will be sufficient to maintain the moveable valve member in the open position. In a preferred form of the invention, the flush valve is located over the outlet with the first portion of the chamber disposed over the moveable valve member such that the moveable valve member can fall under gravity towards the closed position, whereby the initial force of the water exceeds the weight of the moveable valve member tending to close it. Preferably, the one or more ports are located in the side walls of the chamber and are closed by side portions of the moveable valve member which are substantially free of projections tending to interrupt the exit flow of water eg shoulders, lips. The side portions of the moveable valve member may be flush with the interior of the chamber. In the arrangement with the flush valve vertically over the outlet, the lower end surfaces may be substantially tangential to the exit flow of water. Preferably, the moveable valve member is a cylindrical piston with a bevelled surface being provided at the lower end of the piston.

Also described in the specification (but not claimed) is the invention of a flush system including: a closed cistern having a water inlet for connection to a pressurised water supply and a water outlet controlled by a flush valve, said flush valve including a chamber, a moveable valve member within the chamber moveable between a closed position and an open position, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the valve member; an actuation valve operable to drain fluid from said first portion of the chamber to reduce pressure in said portion and move the moveable valve member towards the open position, the chamber being further provided with one or more ports in communication with the remainder of said cistern, a passage between the port(s) and the water outlet being blocked by the moveable valve member in the closed position, the chamber being further provided with a direct opening between the cistern and the remainder of said first portion of the chamber defined over the normal range of movement of the moveable valve member between the open and the closed position.

Suitably, when the system is such that the flush valve is disposed above the valve outlet and the first portion of the chamber is defined in the upper region of the chamber, the opening may be in the form of an aperture provided in the top chamber wall. Brief Description of Drawings

In order that the invention may be more fully understood one embodiment will now be described with reference to: Figure 1 which is a schematic view of a flush system according to a first preferred embodiment of the present invention;

Figure 2 which is a diagrammatic view of the actuating valve of Figure 1 ; Figure 3 which is a cross-sectional view of a flush system according to a second preferred embodiment of the present invention; Figure 4 which is an exploded view of the flush system of Figure 3; and Figure 5 which is a side view of the flush system shown in Figure 3.

Best Modes for Carrying out Invention

The flush system 10 includes a closed cistern 12 which is sealed to be airtight and watertight apart from water inlet 14, water outlet 16, air inlet 18 and actuation valve 20.

The cistern 12 is provided in the form of a shell with a cylindrical side wall 24 closed at a top end by a top wall 26 which is shaped so as to be concave relative to the interior of the cistern 12. The side walls 24 are sealingly connected with a base plate 28 having a threaded central orifice 30. The base of the cistern 12 is also comprised of a central collar having a first externally threaded portion 34 adapted to threadingly engage with threaded orifice 30. The collar 32 also comprises a flanged portion 36 below the first portion 34, the flanged portion 36 defining a shoulder 38 adapted to engage on the underside of base plate 28. A peripheral seal in the form of an 0-ring 40 is provided along the shoulder 38. The collar 32 has a central aperture 42 defining the outlet 16 of the cistern.

The outlet 16 is controlled by a flush valve 50 disposed above the cistern outlet 16. The flush valve 50 provides a substantially cylindrical flush chamber 52 defined by a cylindrical chamber wall 54 and a top chamber wall 56. A moveable valve member in the form of a substantially cylindrical piston 60 is disposed in the chamber 52, the external diameter of the piston 60 being substantially commensurate with the internal diameter of the side wall 54, although a small clearance may be provided between the two to assist with movement of the piston. The piston 60 may be of the shell type having a hollow cup- shaped form which is ordinarily full of water. The piston 60 may have a toothed top edge (not shown). The piston 60 is shown in the closed position above which is defined an upper portion 62 of the valve chamber 52. The top chamber wall 56 has an opening 64 allowing for flow of water between the main portion of the cistern 12 and the upper portion 62 of the valve chamber 52. The opening, for a cistern operating at a standard pressure of 50 psi with a lightweight aluminium piston is preferably 1.8 mm. The opening size could range between about 1.5 mm and 2.0 mm.

Located in the base of the side wall 54 are a number of ports 66 into the chamber 52 although they are closed when the piston 60 is located in the closed position as shown in the drawing. The skilled reader will appreciate that the outlet 16 is also closed when the piston 60 is located in the closed position. Thus, in the closed position the piston 60 blocks passages between the ports 66 and the outlet 16. Only two ports 66 are shown in the drawing but it will be appreciated that more of such ports may be provided along the periphery of the side wall 54. It is preferred that such ports are provided in diametrically opposed pairs. The base of the piston has a chamfered edge as shown, seated in a complementary shaped valve seat. A portion of the chamfered edge may extend beyond the valve seat to provide a region on which an upwards component of the exit force of water can be resolved.

The actuation valve 20 is also schematically depicted in the drawing. It can be seen that fluid from the upper portion 62 of the chamber 52 will be permitted to flow along conduit 72 when the actuation valve 20 is operated. The passage 72 may drain into the central aperture 42 provided in the collar 32.

The water inlet 14 is provided by way of an upright conduit 22 through the base plate 28. The conduit 22 is connected to a pressure reducing device (not shown) which ensures that the water entering the system is at a standardised pressure eg 50 psi. A reduction in diameter may be provided in the mains supply inlet eg 1.5 mm. This inlet diameter may be varied for different installations and affects the refill time for the system.

It can be seen that the water inlet 14 is located above the maximum water level 80, the existence of which will be explained in due course and as well as affecting the refill time for the system, influences piston closure.

As will be appreciated from a discussion of the operation of the system, it is necessary to maintain a certain quantity of air within the cistern 12. Some air losses can occur during rapid flushing of the cistern. Further, the pressurisation of air which occurs during operation can also cause some of the air molecules to be dissolved into the water and thus lost during flushing of the cistern 12. The air inlet 18 is therefore provided to supplement air into the cistern 12. The air inlet valve is closed when the water level reaches over the level of the air inlet 18. In fact, some water may escape through this valve until the valve is fully closed.

The operation of the cistern 12 will now be discussed. Water enters the cistern 12 through the cistern inlet 14 thereby increasing the pressure within the cistern 12. As mentioned, the air inlet will remain open until water rises above the inlet and a predetermined pressure (eg 20 psi) is achieved. When the air inlet closes, the water level will have reached above the top of the air inlet but is someway below the maximum level 80. Water will continue to enter the cistern 12 thereby compressing the quantity of air trapped within the cistern until the air pressure reaches an equilibrium with the pressure of the incoming water, at which point no further water enters the cistern 12. This equilibrium point defines the maximum water level 80. It will be pointed out that the water inlet 14 is located at least some 10 centimetres above the maximum water level 80. This safeguards against backflow of water in the cistern 12 into the water supply. If a negative pressure is created in the water supply, the non-return valve prevents loss of pressure in the cistern.

When the equilibrium point is reached such that the water level is at the maximum level 80, the cistern 12 is ready for flushing. Pressurised water will also be present in the upper portion 62 of the chamber 50 since water is permitted to flow through bleed hole 64. To initiate the flush, the water in the upper portion 62 is opened to the atmosphere via the actuation valve 20 and water is drained from the upper portion 62. Of course water is still permitted to enter the upper chamber through opening 64 but the dimensions of this opening and the operation of the actuation valve is such that there is a net pressure loss in the upper portion of the chamber which causes piston 60 to rise and at least partially open the ports 66.

Water will exit rapidly through the passages defined between ports 66 and the outlet 16.

The initial force of the rapidly exiting water will urge piston 60 upwardly. The piston 60 has a bevelled lower edge 82 which assists in maintaining the piston in the upper position, until the flow decreases to the extent that the piston is able to fall under its own weight.

The opening 64 functions to ensure that there is no negative pressure tending to hold the piston up. In the operating environment with water entering the cistern during the refill part of the flush cycle, water and air enter the chamber portion 64 assisting with the establishment of a force balance returning the piston 60 into the closed position. As can be seen from the drawing, the piston 60 is hollow with an open top 84. Thus water will be maintained within the hollow portion of the piston 60. During flushing, the pressure within the cistern will drop below the equilibrium pressure enabling water to again enter the cistern through the water inlet 14. However, the rate of entry of water into the cistern is significantly less than the flow rate of water out of the cistern 12. At a latter part of the flush cycle, the water level and the pressure within the cistern will be such that the piston is permitted to drop under gravity. Any negative pressure in the space above the piston will be overcome by water and/or air entering the valve chamber through the opening 64 in the top wall 56. As the piston 60 drops, it closes ports 66 and as pressure again builds up within the cistern 12, the piston 60 will be held closed. The cistern 12 then fills until the equilibrium point is reached and the system is again ready for flushing.

It can be seen that the present invention achieves pressurised flushing with simplicity. There are few moving parts, most of which are controlled by differential forces operating within the cistern. This balance of differential forces must be carefully maintained. It is desirable to control the inlet pressure to a standardised pressure in order that other operating parameters of the system can be tuned to this particular pressure eg opening size (64), piston weight. As a further example, it is desirable that the actuation valve 20 is able to fully discharge line 72 to obviate a back pressure in line 72. To this effect, if the actuation valve 20 is to be connected to the outlet 16, it should be connected in such a way that does not deleteriously affect the balance of forces in the chamber above the cistern.

As mentioned, the piston 60 is hollow. It is envisaged that a solid or closed piston could also be utilised to achieve satisfactory operation of the valve provided that the subtle balance of forces is maintained. If the piston 60 is too heavy, the piston will not rise on operation of the actuation valve 20.

Figure 3 illustrates an alternative form of a flush system 10a. Some of the components are similar to those in the first embodiment and like numerals represent like parts. The flushing system 10a includes a cistern having a cylindrical side wall 24a closed at the top end by concave top wall 26a. The form of the cistern is not limited to being cylindrical.

The substantially cylindrical piston 60a is provided in a valve housing 90a which may be clamped to the cistern 12a by a removable clamp 92a. The housing 90a provides a cylindrical chamber 52a in which the cylindrical piston 60a is provided. Unlike the previous embodiment, the piston 60a is moveable horizontally, perpendicular to the length -wise direction of the cistern 12a. The chamber 52a includes an outlet 16a and an inlet passage 66a. The inlet passage 66a is located in the top wall of the chamber 52a in communication with the interior of the cistern 12a. In the closed position of the piston 60a, the piston is seated against valve seat 94a. The forward end of the piston which engages with the valve seat 94a has a bevelled edge 95a. The top wall of the chamber 52a is also provided with an opening 64a communicating between the interior of the chamber behind the piston 60a and the interior of the cistern 12a. Suitably, the opening 64a is open for all normal positions of the piston 60a, the spring 97a and rear of actuation member 103a preventing the piston 60a from obstructing the opening 64a. The opening 64a is in fact optional since with injection moulded components the tolerance is such that a space will be provided between the piston 60a and the chamber wall sufficient to define a bleed passage therebetween.

It can be seen that the piston 60a is hollow with a central aperture provided at the forward end of the piston 60a, behind which is a bore reducing in diameter towards the rearward direction of the piston 60a and terminating in an actuation valve seat 100a at which is seated an actuation valve 101a. The actuation valve may be operated by an actuation means comprising a slide member 102a and an actuation member 103a extending through the central bore and forwardly of the piston 60a. The slide member engages with a depressible plunger 104a. The slide member 102a and the depressible plunger 104a have mutually inclined engagement surfaces so that when the depressible plunger 104a is moved downwardly, the actuating member 103a is moved to the left, according to the drawing of figure 3, to move the actuation valve 101a away from the actuation seat 100a and thereby reduce the water pressure in the chamber 52a behind the piston 60a. As explained in the previous embodiment, this causes the piston 60a to move to the left whereupon the valve is open and water exits the cistern 12a.

The slide member 102a is held in place by the inner sleeve 115a which also supports the valve seat 94a.

The operation of this embodiment will now be described. Water at mains water pressure enters system via a pressure limiting device (PLD) 105a which limits water pressure to 50 psi. This pressure can be varied and is expected to be between 40 and 50 psi. The pressure limiting device may also operate as a non-return valve to prevent loss of system pressure even when the water is turned off, or as an alternative, non-return valve may be included in the water inlet line.

A feature of the invention includes an aperture (not shown) in the water inlet line to the cistern to control incoming water volume (velocity) which in association with the cistern volume and area of outlet port 16a from the piston chamber influences the piston closure.

We have also confirmed that a fine balance exists between the velocity of the water flow into the cistern, the volume of the cistern and the area of the exit aperture 66a into the piston body when the piston is open.

If the incoming water velocity is too high, complete emptying of the cistern does not occur even with extended flush time. This appears due to a venturi effect occurring in the piston opening restricting water at the now reduced pressure from exiting the cistern. Optimum operation is achieved by fine tuning the incoming water velocity by reducing the water inlet diameter. This must be located after the reduction in mains pressure by the pressure limiting device 105a. The optimum water velocity achieved by varying the inlet diameter is specific for a particular cistern volume.

Water from PLD 105a enters the cistern 12a through a water inlet riser 14a which terminates 3-5cm from top of the cistern 12a and sprays water onto the curved top wall 26a, spreading water impact. The cistern 12a fills with water until the air therein is compressed to pressure set by PLD 105a - nominally 40 psi. This results in an air gap at the top of the cistern 12a above the water level, 8-10 cm in depth, subject to the water pressure.

In this situation, i.e., when the cistern 12a contains water under pressure the piston 60a is held shut against rubber valve seat 94a, sealing the system closed and preventing water leakage.

To activate a toilet flush, the plunger 104a is depressed (against the action of spring 109a) and held down forcing actuator member 103 through the centre of the piston pushing the actuation valve off the actuation valve seat 100a at the rear of the piston. This opens the space at the rear of the piston to atmospheric pressure allowing the initial escape of pressurised water from the rear of the piston into adaptor 107a.

This produces a relative pressure drop behind the piston 60a which is pushed back (against optional spring 97a) allowing water under pressure to exit through outlet 16a via adaptor 107a to toilet pan.

On release of plunger 104a, spring 97a pushes actuator valve 101a to actuation valve seat 100a at which time water under increasing pressure (as cistern 12a automatically refills) enters rear of piston cavity via opening 64a and/or along the sides of piston 60a in space between the piston and the chamber walls, holding piston 60a against seat 94a stopping the outflow of water and allowing the cistern 12a to fill to the required pressure as determined by PLD 105a.

This very effective pressure seal prevents water leakage from the system. Assembly and service, including replacement of components, is achieved by unscrewing threaded nut 110a allowing removal of parts from the housing 90a. Unintentional withdrawal of the plunger 104a is achieved by retention tab 113a.

Although the flush can be actuated by manual depression and holding down of plunger 104a for the duration of the flush (typically 6-8 seconds) the preferred option is to electronically control depression and hold down of plunger 104a for selected time periods typically between 2-12 seconds.

With this electronic control in the form of solenoid 11 la a range of push buttons (likely maximum of two) can be provided to activate different (selected) flush periods (i.e., hold down times for plunger 104a providing flush volumes between 2 and 10 litres only subject to the total volume of cistern 12a. For example a full flush option may be typically 5 litres with a 'half flush option of 2 litres. The push buttons may be remotely located from the flush system.

Thus the Ecoflush system has an inbuilt capacity to provide full and half flush volumes for toilet flush systems and due to the pressurised water flush volumes as low as 2 litres achieve a flush equivalent to gravity fed systems.

The push button flush actuation switch can be located at any point adjacent to or remote from the system location but requires connection to the electrical mains supply. The incorporation of the electronic control allows concurrent switching of auxiliary devices such as a toilet fan which could operate for a predetermined limited time.

An operational advantage of the system is the fast and low noise level refill operation.

This pressurised toilet flush system can be located within a wall cavity or on a wall surface with the required cover plate provided as part of the system package.

Claims (13)

CLAIMS:

1. A flush valve for a flush system, said flush valve including: a chamber provided with one or more inlet ports and an outlet; a moveable valve member within the chamber moveable between an open position and a closed position blocking passage between the inlet port(s) and the outlet, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the moveable valve member; and an actuation valve operable to drain fluid from said first portion of the chamber to reduce pressure in said portion and move the moveable valve member towards the open position, the actuation valve being operable by an actuation means extending from the outlet side of flush valve through the moveable valve member.

2. The flush valve as claimed in claim 1 wherein the actuation valve is disposed at the first end of the moveable valve member.

3. The flush valve as claimed in claim 1 or claim 2 wherein the moveable valve member is in the form of a cylindrical piston and the actuation means extends in substantial alignment with the central axis of the piston.

4. The flush valve as claimed in any one of the preceding claims wherein the actuation means is operable by a plunger member, the actuation means and the plunger member having mutually inclined engagement surfaces.

5. The flush valve as claimed in claim 4 wherein the plunger member is oriented substantially perpendicular to the longitudinal axis of the actuation means.

6. A flush system including the flush valve as claimed in claim 5 wherein the moveable valve member is oriented for substantially horizontal movement thereby enabling the plunger member to extend in a substantially upright manner.

7. The flush system as claimed in claim 6 or a flush system including the flush valve as claimed in any one of claims 1 to 4 wherein an electronic control means is provided to control operation of the actuation valve.

8. A flush system including; a pressure reducing valve for connection to a pressurised water supply, the pressure reducing valve adapted to reduce water pressure to a predetermined pressure; a closed cistern having a water inlet for continuous connection to the water supply downstream of the pressure reducing valve and a water outlet controlled by a flush valve, said flush valve including a chamber, a moveable valve member within the chamber moveable between a closed position and an open position, the moveable valve member in the closed position defining a first portion of the chamber at a first end of the valve member; an actuation valve operable to drain fluid from said first portion of the chamber to reduce pressure in said portion to move said moveable valve member towards the open position; the chamber being further provided with one or more ports in communication with the cistern, a passage between the one or more ports and the water outlet being blocked by the moveable valve member in the closed position, the chamber being provided with a bleed passage between the cistern and said first portion of the chamber.

9. The flush system as claimed in claim 8 wherein the bleed passage is defined in the chamber wall.

10. The flush system as claimed in claim 8 wherein the bleed passage is defined between the moveable valve member and the chamber wall.

11. The flush system as claimed in any one of claims 8 to 10 wherein an electronic control means is provided to control the operation of the actuation valve.

12. The flush system as claimed in claim 11 wherein the control means provides for a variable duration of flush.

13. The flush system as claimed in claim 11 or claim 12 wherein the electronic control includes a user actuator, remotely located from the actuation valve.