APPARATUS FOR SWITCHING BETWEEN MAINS WATER AND STORED WATER SUPPLIES BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to devices and methods for interfacing mains water and pumped water supplies, for example rainwater collected in a rainwater tank. 2. Description of Related Art [00021 Australian Patent Nos. 2003262296 and 2005101017 disclose a device for switching the water supply for a property between the mains water supply and a rainwater supply, depending on both the amount of demand detected and the availability of the rainwater in the tank supplying the rainwater pump. The device includes a demand sensor, an input for a sensor detecting the availability of the rainwater, and a valve for switching between the mains water and rainwater supplies. When the demand is below a threshold level, the water to the building is sourced solely from the mains supply, while above the demand threshold the water is preferentially sourced from the rainwater supply if available, or if this is not available then from the mains water supply. [0003] The switching may be by means of an electrically operated solenoid, or alternatively by a combination of a pressure reduction valve fitted to the mains supply and a non-return valve. [0004] Shortcomings of these arrangements include the need to incorporate power circuitry to the device for demand sensing and switching and, in the pressure reduction switching arrangement, the limited mains water pressure which is provided to the premises.
SUMMARY OF THE INVENTION [0005J The present invention seeks to provide an alternative. [0006] In one form, the present invention provides a switching device for controlling switching between a mains water supply and a stored water supply - such as a rainwater storage tank - of a premises, including a valve pilot responsive to presence of pressure from a pumped rainwater supply and a hydraulically-operated valve actuated in response to actuation of the pilot to close off the mains water supply. 10007] Further forms of the invention will be apparent from the claims, and from the description below. BRIEF DESCRIPTION OF THE DRAWINGS [00081 Further preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: [0009] Fig. 1 is a schematic general arrangement of a switching arrangement according to a first preferred embodiment, as used in conjunction with two different pumping and arrangements; [0010] Figs. 2A to 2C are orthogonal views of a switching device according to a second preferred embodiment; [00111 Figs. 3A to 3C are cross-section elevations taken along lines A-A, B-B and C-C respectively of Fig. 2C; [0012] Fig. 4 is a parts list for Figs. 3A to 3C; [0013] Fig. 5 is a perspective view of the embodiment of the device of Figs. 2A-2C; and [00141 Fig. 6 is an exploded view of the switching device of Figs. 2A to 5; 2 DETAILED DESCRIPTION OF THE EMBODIMENTS [0015] Fig. 1 schematically illustrates a water supply arrangement for a house 103 or other premises, including an electrically driven pump 101 with a demand-sensing pump controller 108, a pump outlet pipe 106 leading to'a rainwater inlet of a switching device 102. j0016J The pump 101 draws from a rainwater storage tank 107, either via a tank outlet flange located in the tank side wall just above the bottom of the tank, as shown at the left side of Fig. 1, or via a suction tube as shown at the right side of Fig. 1. In a variant to the arrangement at the right side of Fig. 1, the pump may be of the submersible type and submersed in the water rather than located above the tank and connected via the suction tube as illustrated. [00171 The switching device 102 has a further inlet 105 attached to the mains water supply, and an outlet 104 connected to the water supply plumbing of the premises 103. [0018] The pump controller 108 may be of the commonly-employed type, including a flow or pressure sensor which senses demand caused by opening of an outlet in the premises - such as turning on a tap or refilling a toilet cistern - and switches on power to the pump 101. [0019] As is also commonly employed in pump controllers, the controller further has a mechanism for detecting a lack of water supply to the pump, for example if water to the pump is interrupted or the tank level is too low, and switching to a mode in which power to the pump is disabled until the controller is reset. [0020] Preferably, in one embodiment of the invention, the pump controller further includes an auto-restart capability, whereby upon the controller detecting lack of supply and switching off the power, the controller subsequently attempts to restart. This may be controlled for example by a timer function, so that the controller may attempt to 3 restart for example every 24 hours, or some greater or lesser period. In this way, the pump is again enabled if the rainwater supply again becomes available, such as when more rainwater is collected in the tank 107, without needing to be reset by the operator. [00211 An example of a pump controller with an auto-restart capability is the DAB ACTIVE from White international Pty Ltd of Milperra, Australia. [0022] The restart timing may be uniform, or may for example have a shorter period for initial restart attempts then switch to a longer restart period if a certain number of unsuccessful attempts has been exceeded. [0023] Use of a self-priming pump is strongly preferred. [0024] Figs. 2A to 6 illustrate a switching unit according to one embodiment of the invention. Major components of the device are denoted with circled reference numerals, and are listed in the parts list table at Fig. 4. [00251 The switching unit has an external housing, preferably moulded of plastics material such as nylon in two or more parts, having openings for a rainwater inlet connection, a mains water inlet connection and an outlet connection leading to the water supply of the premises. [0026] In the illustrated form, the switching device housing comprises three main portions - a central base portion 1, a cover 2 and a bottom portion 10 - which house the check valves 3, mains water diaphragm valve comprising components 7 to 9 and the pilot valve assembly comprising components 12 to 17, which operate as described below. 100271 The base portion 1 comprises a junction and valve housing component which forms the water passages of the junction between the two inlets and the water outlet and which houses the valves and other mechanisms of the unit. 4 [00281 In one preferred form, at least the base component 1 is of moulded plastics material, such as nylon or the like, and configured specifically to form water flow passages of the unit and to receive the valve mechanisms of the unit. [00291 At the mains water inlet end, the junction component 1 includes an internal chamber for receiving two check valve assemblies 3 for preventing backflow of water into the mains system, and a threaded connection for a union nut 4 for securing a union pipe 5 for connection to the mains supply. The union nut 4 and union pipe 5 are optionally also formed of polymeric material such as nylon. [0030] At the stored or rainwater inlet, underneath the housing, the junction component includes a chamber for housing a check valve assembly 3B for the rainwater/ stored water supply, but provision for more than one can be readily made. A valve stop sleeve is used to mechanically hold check valve 3B in its place in the housing 1. [0031] An O-ring 25 provides a seal between housing portions 1 and 10 at the stored water or rainwater inlet in such a way as to provide pressurization of the pilot by inlet pressure only, that is not by mains pressure, and thus the reason that the check valve assembly 3A is utilised. [0032] The stored water or rainwater inlet is also provided with a union nut 4A and union pipe 5A for forming the connection to the rainwater supply from the pump 101, and a strainer 6. [0033] The junction and valve housing component I also provides an outlet connection leading to the house, via a further union nut 4B and union pipe 5B. [0034] The union nuts 4, 4A, 4B, union pipes 5, 5A, 5B, housings 1, 2, and 10 etc are designed so that the check valve assemblies 3, 3A and 3B, and others which may be used, are readily accessible for maintenance. 5 [00351 While the inlet and outlet connections are shown as employing nut and pipe connectors, any suitable connection arrangement which meets the appropriate standards may be substituted, however these should preferably allow ready access to the check valve assemblies used. 10036] The junction and valve housing component 1 further provides the housing for a further valve for switching between supplying mains water or rainwater to the premises, depending on availability of rainwater to meet the demand. [0037] In the illustrated embodiment, the valve comprises a pilot operated, hydraulically actuated diaphragm valve. [0038] The illustrated switching valve arrangement comprises a spool valve arrangement wherein an upper poppet diaphragm 17 is driven by a pilot piston 13 and lower diaphragm arrangement 16 located in a passage communicating with the rainwater supply inlet, to selectively open or close a bleed passage 32 of the diaphragm valve. [0039] The operation of the pilot arrangement will be described further below, and further detail of the pilot valve arrangement and parts may be seen by reference to the cross sections 3A to 3C and the perspective and exploded views (Figs. 5 and 6). [0040] The valve housing component 1 further includes a portion downstream of the respective check valves 3 for regulating the supply of mains water to the house. This portion forms a valve body portion 31 forming a cylindrical cavity 34 - preferably integrally moulded as part of the valve housing 1. - to which is attached a valve bonnet 9 with valve diaphragm 7 and spring 8. [0041] A further, annular cavity 33 adjacent the valve body portion 31, below the diaphragm, communicates with the mains water inlet end, whilst cavity 34 described above communicates directly with the downstream cavity 36, and thus the upwards pressure on th6 diaphragm urging the valve to open is the mains water pressure. 6 [0042] There is a small bleed hole 38 in the diaphragm 6 allowing water to pass between cavities 33 and the cavity 40 above the diaphragm 7. [00431 The cavity 40 above the diaphragm 7 communicates with the downstream cavity 36 via the pilot valve via a passage 32 formed in the valve housing, cavity 35 and another passage (not illustrated) between cavity 35 and the downstream cavity 36, with the pressure above the diaphragm being controlled by the operation of the pilot valve arrangement described below. [0044] The pilot valve comprises a spool 13 controlled by the differential water pressure between that on an upper 17 diaphragm communicating with the passage 32 which is essentially at mains pressure - and on a lower diaphragm 16 exposed to a cavity 42 communicating with the stored water supply in the cavity within valve stop 18 upstream of the check valve 3A, i.e. essentially at the same pressure as the stored water pressure provided to the switching device. [0045] Whilst in practice the pump pressure of the available rainwater/ stored water will usually below the mains pressure, the pilot valve is preferably configured to provide a mechanical advantage to the rainwater side pressure, for example by a proportion of 10:1. For example the lower diaphragm 16 exposed to the stored water pressure in cavity 42 may have a larger surface area than the upper diaphragm exposed to mains pressure in bleed passage 32, and/or the spool may be spring biased. 100461 When the pilot valve is closed due to the presence of pressure from the stored water or rainwater pump acting on the pilot piston diaphragm 20, the pilot valve closes the bleed of water from cavity 40 above the diaphragm to the downstream cavity 36, thus increasing the pressure in the cavity 40 of the diaphragm valve to essentially mains pressure . The diaphragm 7 is thus held closed against the valve member 31 by the force of the valve spring 8, closing off the mains water flow through the diaphragm valve. The rainwater side check valve 3B opens, so that the water supply to the house is sourced from the stored water or rainwater pump. 7 [00471 When the pressure available from the stored water or rainwater pump falls below a certain proportion of the mains water pressure - approximately 1:10 in the illustrated embodiment, though this is adjustable depending on the design of the pilot piston and diaphragms- the spool of the pilot valve is pushed downwards to open the pilot valve and release pressure from the upper chamber 40 of the diaphragm valve. The pressure differential across the diaphragm valve pushes against the valve spring 8 and opens the diaphragm valve to allow flow of water from the mains supply. The mains water is prevented from flowing back to the stored water or rainwater source by closure of the check valve assembly 3A. 10048 Figs 3A and 3B show the pilot valve in this open position, with the upwardly extending cylindrical flange of the upper diaphragm 17 retracted from the tapered end of bleed passage 32. [0049i Thus, in operation of the switching device the water supply to the household is sourced preferentially from the rainwater source when pressure is available, but switched over to the mains supply at essentially full mains supply pressure when there is no pressure or limited pressure available from the rainwater pump. Lack of pressure from the rainwater pump will typically occur because the pump controller 108 has detected insufficient rainwater availability and has switched the pump off, or due to power outage or pump malfunction. [00501 The device may further include an air bleed mechanism, which serves to purge air from the rainwater side of the valve mechanism as may accumulate where the stored water pump switches off following depletion of the stored water supply. 100511 The air bleed mechanism comprising components 19 to 22 comprises a passage 22 (Fig. 3C) extending from the supply side of the stored water check valve 3A up to a cavity which contains a ball float 20. 8 [00521 . In normal operation, where stored water is provided under pressure to the supply side of the check valve 3, the ball float 20 is retained against the valve seat of the air valve cap 19 and blocks off the air valve passage which leads to the air purge tube 21. However, where the stored water has been depleted, it may often be the case that air is trapped between the rainwater pump and the supply side of the switching device before the pump switches off. In this situation, the cavity in which the ball float sits will be full of air and the ball float will not close against the valve seat. Therefore, as the stored water pump attempts to restart, the trapped air will be purged through the air tube 21 as the pump is restarted. When purging of the air is completed, the cavity will fill once again with water, the air valve closes and normal operation of the switching device resumes, with the pressure from the stored water supply causing operation of the pilot valve and diaphragm valves to block the mains water as previously described. [00531 Fig. 3C shows the air purge valve open, with the ball 20 spaced from the valve seat formed by the end cap 19, whereas in normal operation of the device the air valve will be closed. [0054J The device may further include a support bracket 44, such as that visible in Figs 2B, 2C and 6, for attachment to a building or other structure. [0055] When used in conjunction with a pump controller having an auto-restart capability, as described above, the illustrated switching device arrangement allows the household water supply to switch over to mains supply when the rainwater has been consumed, and to check periodically for replenishment of the rainwater supply, and to switch back to rainwater when again available, without needing a manual restart of the pump. [0056J The construction of the switching apparatus, including a moulded component forming the T-junction and valve housings, is also considered to be novel and useful, and to save on time and cost of manufacture. 9 100571 In an unillustrated embodiment, the device may also contain additional components, including a female power point outlet, cable glands and/or an electrical terminal block, to allow the unit to provide an auto-restart capability for installations where the pump controller 108 does not have this capability. [00581 In such an embodiment, electrical power may be provided through one of the cable glands to connect to the terminal block, and fed back out via a switching arrangement (not shown) to the power outlet, from which the pump controller electrical power is drawn. The switching arrangement may comprise a timer circuit for attempting periodic restart of the pump, or may comprise a switch attached to a tank level sensor (not shown), such as a float switch or pressure sensor detecting the level of rain water in the tank. 100591 A port is provided for the connection of a water storage pressure vessel to be fitted as an option. This port is fitted with a blanking plug 11. The port enables connection of another device such as a garden hose to be attached after the switching device 102 has been plumbed into the household supply system. Further it can be used as a connection port for a pressure tank which can provide a buffer of pressurised water thus preventing the pump from starting in order to supply small quantity of water such as a single cup or glass or a leaking toilet cistem. [0060] While the above description details the use of the switching device 102 with a stored water or rain water system having a pump to provide pressure, this can be readily substituted with a source of rain water or stored water which is made available to the switching device 102 under pressure to being located at a positive height differential relative to the switching device 102. [0061J In this specification, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of'. A corresponding meaning is to be 10 attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear. [00621 While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. It will further be understood that any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates. 11