WO2009001093A2

WO2009001093A2 - Water saving systems and/or methods

Info

Publication number: WO2009001093A2
Application number: PCT/GB2008/002200
Authority: WO
Inventors: Mark Anthony James Ward
Original assignee: Mark Anthony James Ward
Priority date: 2007-06-27
Filing date: 2008-06-26
Publication date: 2008-12-31
Also published as: EP2174066A2; WO2009001093A3; GB2441025A; GB2441025B; GB0712480D0

Abstract

A water saving system (10) comprises a pump (12) operatively connected to a water line (18) leading to a hot water outlet; means for detecting a demand of hot water (116) at said hot water outlet (16); means for triggering the operation of said pump (12) in response to the detection of said hot water demand; whereby said pump (12) draws water in said water line (18) towards a cold water storage tank (120) such that the water line is purged; means for detecting the arrival of air (114) at a point of said water line; means for switching off said pump in response to said arrival; said pump or an additional pump being operatively connected to said water line leading to a hot water outlet (16); and means for switching on said pump or an additional pump following said arrival in order to refill said water line with hot water,- whereby hot water is delivered at said hot water outlet (16).

Description

Water Saving Systems and/or Methods

Field of the Invention

This invention relates to water saving systems and/or methods.

Background and Prior Art known to the applicant

The following prior art is acknowledged:

EP 38318 AUSTRIA EMAIL-EHT AKTIENGESELLSCHAFT

EP 38964 FORBACH GMBH & CO. KG

EP 85774 GOSSI, HANS EP 1 19585 RUHRGAS AKTIENGESELLSCHAFT

EP 122475 STUTTGART HEIZ LUEFT KLIMATECH

EP 279639 HOT WATER EQUIPMENT CORPORATION

EP 306235 INAX CORPORATION

EP 452259 DOMOTEC AG EP 472276 ELECTRICITY ASSOCIATION SERVICES LIMITED

EP 544207 WIRNSHOFER, KLAUS EP 674137 SPIEGEL, HERBERT EP 936415 ROBERT BOSCH GMBH EP 1158251 VAILLANT GMBH EP 1249666 ROBERT BOSCH GMBH EP 1408282 DALKIA FRANCE EP 1447626 WOLF GMBH CB 378486 PERFECTIONNEMENT DE LA CHAUFFE CB 480883 PENBERTHY INJECTOR COMPANY CB 508258 MARCEL CROSSEN CB 535230 HOWARD JOHN FOUNTAIN CLARKSON THIMBLE TUBE BOILER C

CB 615235 HENRI BORCHESAN CB 679160 GUSTAVSBERGS FABRIKEN AB CB 696710 VAPOR HEATING CORP CB 914786 RHEOSTATIC CO LTD CB 980499 ASCOT GAS WATER HEATERS LTD CB 1042360 INGEMAR FILIP PAULUS WOLFF CB 1062746 WILLI BRANDL CB 1116208 SPIRAX SARCO LTD GB 1157134 - not available - CB 1205706 - not available - GB 1221965 - not available - GB 1236834 - not available - CB 1269128 - not available - GB 1285126 - not available - GB 1328262 HAWKLEY B PAVELEY A J GB133968Z VAILLANT KG JOH GB 1429317 HEATING EQUIPMENT LTD GB 1485881 WARDT GB 1543546 HONEYWELL BV GB 1582268 CHAFFOTEAUX ET MAURY GB 1592008 TOUR & ANDERSSON AB GB 1595319 ENVIRONMENT SECRETARY OF STATE FOR GB 2028986 IMI RYCROFT LTD GB 2153499 WORCESTER ENGINEERING COMPANY LIMITED GB 2153502 WORCESTER ENGINEERING COMPANY LIMITED GB 2205357 STUART TURNER LTD GB 2219497 POWERED SHOWERS PLC GB 2226388 LUDWiG LUDIN

JOHANNES NIKOLAUS LAING GB 2234294 ROBERT LEITCH RIVERS GB 2251709 PETER FREDERICK WAILING SYDNEY RICHARD MITCHELL

GB 2298480 NEVILLE IAN BENSON GB 2322929 INTER ALBION LIMITED GB 2336422 MIDLAND TOILET HIRE LIMITED GB 2348945 DOUGLAS INDUSTRIAL LIMITED GB 2356691 KOMFORT 2001 LTD GB 2361295 THE HONG KONG AND CHINA GAS CO. LTD GB 2364766 NICHOLAS JULIAN JAN FRANCIS MACPHAIL GB 2369877 STEVEN CAFFAL FINCH GB 2376517 LUBOR SCHILLER GB 2382646 GLEDHILL WATER STORAGE LIMITED CB 2413623 FABDEC LIMITED

US 3647136 JOH. VAILLANT KG.

US 3705574 A.O. SMITH CORP.

US 4241588 FLEETWOOD, ANSLEY R MURPHYJIMMY

US 4441902 KAMAN SCIENCES CORPORATION us 4529032 MOLITOR INDUSTRIES, INC. us 4562956 CHECK; ROBERT F us 4599992 HARDING; JOHN W US 4606325 LUJAN₁ JR; ALBERT G.

US 4747273 ARTESIAN BUILDING SYSTEMS us 4750472 FAZEKAS; DALE J us 4917142 LAING; NIKOLAUS L LUDIN; LUDWIG US 4921 163 VIESSMANN; HANS US 4936289 PETERSON; GEORGE A US 4945942 METLUND ENTERPRISES US 5009572 SEIF; SADRADDIN IMHOFF; RAY US 5020721 GAS FIRED PRODUCTS US 5056712 ENCK; HARRY J US 5105846 BRITT; PAUL E US 5205318 SJOBERG INDUSTRIES, INC. US 5261443 WALSH; PAUL F US 5277219 METLUND ENTERPRISES US 5351337 DEUTSCH; JOSEPH J US 5351712 HOULIHAN; JOHN A US 5511579 PRICE; WILLIAM D US 5584316 ACT DISTRIBUTION, INC. US 5735291 KAONOHI; GODFREY K US 5775372 HOULIHAN; JOHN A 5 US 5829467 SPICHER; VINCENT M US 5941275 LAINC; KARSTEN ANDREAS US 5944221 LAINC JOHANNES KIKOLAUS LAINC; KARSTEN ANDREAS

10 US 6039067 HOULIHANJ JOHN A US 6182683 TEMTROL, DELTA T. INC US 7077155 GIAMMARIA BRUNO US 2002139420 EBSTER WILFRIED US 2003089399 ACKER LARRY K

15 US 2004182439 S.P.CE. LTD US 2005001046 LAING OLIVER US 2005183778 PEARSON KENNETH W. JR. WO 8301499 VAN DEN BOS, GERRIT WO 8505576 MOLITOR, VICTOR, D

20 WO 9300559 CHOIJIN. MIN WO 9963278 DANFOSS A/S WO 2001 13045 WALDER GERHARD LEITER, KLAUS

WO 200212125 BATTELLE MEMORIAL INSTITUTE 25 WO 2004070279 STIRN₁ DOUGLAS, ROGER WO 2004088051 WILLSFORD₁ ANDREW, DONALD MURRAY, CHRISTOPHER, JAMES

WO 2005057086 RINNAI CORPORATION RINNAI AUSTRALIA PTY LTD WO 2005071322 KROON, ARIE

WO 2006002477 POLDMAA, ARVO

WO 2006111755 CLEAN HEAT PROVISION LIMITED

GB 2290857 ROBIN TWINE CB 2427259 DERICK SINCLAIR

US 6,032,687 LINN

GB 2418725 DERECK SMITH ET AL

The problem of water wastage has long been known, but has largely been ignored due to a seeming superabundance of it. Such an attitude now seems complacent in the light of the multi-faceted environmental concerns of which we are gradually being made aware in the

Western world and elsewhere. In particular, daily prognostications of climate change have made us acutely aware of the contingency of the water supply in a particular locale. One can also see this new awareness of water as a result of its co-modification. That is to say that water can now be purchased in a variety of guises and forms in retail outlets, and this placing of value has been transferred from such products to water in general. What before was considered free and plentiful, is now thought of as of valuable and limited. This confluence of environmental and social currents has begotten a widely felt need to find ways of conserving water. This need is particularly felt at the level of the individual conscience.

A further environmental issue is raised by the wasting of hot water, which is that clearly said hot water costs money and energy to heat. Savings on both are advantageous to the individual and to the planet, and are similarly sought after.

It is an aim of this invention to address the problems of water and energy efficiency.

The problem of the delivery of instant hot water is known. Patents are numerous around

"circulation pump" technology, which, as the name suggests, circulates the water around a predetermined hot water system, bringing all water in the system periodically into contact with heating means. Examples of this technology may be found in patent specification numbers US 493 6289 PETERSON and US 494 5942 LUND, and in the products of Bell and Gossett, amongst others.

Circulation pumping systems are, however, exceedingly energy inefficient. Continuous or even timed circulation systems have only an inductive relationship with the usage pattern of a given present. As such, they waste a lot of energy circulating water in order to keep it hot, when no water is being demanded at all. The energy that is wasted is the electricity used to power the pump and to keep the water heated. This is costly to the person paying for electricity bill, and more importantly is damaging to the environment, as waste is effectively traded for greater waste.

It is an aim of this invention to provide means for fast and efficient hot water delivery which is relatively energy efficient.

The nearest prior art is US 5105846 BRITT, which discloses means of removing a "slug" of cooled water from the hot water line, prior to the supply of hot water. This specification is problematic and possibly dangerous, because it prescribes that the cooled hot water be pumped into the cold water line.

It is an aim of this invention to provide means for saving the cooled hot water without having to taint a cold water line.

All of these aims need to be achievable on the level of the individual user or operator - who for the purposes of this specification is a man - his family, and community. Any system, method or apparatus for saving water should be easy to install and operate, and be cost effective. Ideally it should come in a single, relatively small container, be made of easily locatable parts and require a minimum number of connections.

It is an object of the present invention to attempt to solve these problems, amongst others. Summary of the Invention

In a first broad independent aspect, the invention provides a water saving system comprising a pump operatively connected to a water line leading to a hot water outlet; means for detecting a demand of hot water at said hot water outlet; means for triggering the operation of said pump in response to the detection of said hot water demand; whereby said pump draws water in said water line towards a cold water storage tank such that the water line is purged; means for detecting the arrival of air at a point of said water line; means for switching off said pump in response to said arrival; said pump or an additional pump being operatively connected to said water line leading to a hot water outlet; and means for switching on said pump or an additional pump following said arrival in order to refill said water line with hot water; whereby hot water is delivered at said hot water outlet.

In a subsidiary aspect, said means for detecting a demand for hot water incorporate a pressure switch.

In a further subsidiary aspect, said means for detecting a demand for hot water incorporate a flow meter.

In a further subsidiary aspect, said means for detecting the arrival of air incorporates a pressure switch.

In a further subsidiary aspect, said means for detecting the arrival of air incorporates a flow meter.

In a further subsidiary aspect, a thermostatic mixing valve is provided in association with said additional pump.

In a further subsidiary aspect, said pump is configured to draw water from said water line to said cold water tank and said additional pump is configured and of relatively lower power than said pump to refill said water line with hot water. In a second broad aspect, the invention provides a water saving system comprising: a pump operatively connected to a water line leading to a hot water outlet, which when energised pumps water from said water line; a controller for triggering the operation of said pump dependent on a predicted or sensed temperature level; characterised in that said system further incorporates a purge line which interconnects said water line and a cold water storage tank.

It achieves the following advantages:

1) Providing an alternative way of saving the cooled water which is usually left in hot water lines after a demand for hot water has been satisfied; the alternative way allowing the system to be readily retro-fitted to existing water systems and readily scalable to operate in conjunction with either a single hot water outlet or a plurality of hot water outlets.

2) Avoiding the pollution by the purged water of the cold water line, and the attendant risks, both to the health of people using the cold water line, and to the system itself.

3) Keeping "drinking water" from bacterial and parasitic contamination induced by the purged water; which marks a complete departure from the prior art teaching of feeding the purged water directly into the cold water main supply.

4) Keeping "drinking water" from hot water induced pollution; which again marks a complete departure from the prior art teaching of feeding the purged water directly into the cold water main supply which may cause pollution through the transportation of lead or plasticizers often generated during the operation of the hot water line;

5) Keeping "drinking water" from the potential introduction of scale produced in the hot water line more quickly than in the cold water line.

6) Keeping "drinking water" from potential atmospheric contamination; which again marks a complete departure from the prior art teaching of feeding the purged water directly into the cold water main supply which may cause contamination when for example in older houses, the header tank connected to the hot water line may open into the atmosphere, leading to a risk that the water becomes tainted with animal droppings and even carcasses. The invention avoids the risks of introducing these undesirable foreign bodies into the cold water line, which is generally the line from which people drink.

7) Energy savings associated with the pump when deployed in systems where the mains cold water lines are pressurised. This also marks a complete departure from the prior art teaching of the Britt system which requires relatively high pumping power to force the purged water into the pressurised mains, which would effectively neutralise any energy savings which had been garnered through the saving of the water;

In a subsidiary aspect the system is arranged in such a manner that said pump or an additional pump is operatively connected to a water line leading to a hot water outlet to deliver hot water to said hot water outlet following purging of said line.

Advantageously, embodiments with this feature have a means of ensuring that a purged line is replenished relatively quickly. The operator does not therefore have to wait for the hot water to flow from the tank at its usual speed - it is positively pumped to him. It also allows potential air locks to be overcome.

In a further subsidiary aspect, the system further comprises means for permitting flow through said purge line from said hot water line only toward said cold water tank.

It is also advantageous in that it ensures there is no "backwash" of water from the cold water tank to the hot water line.

In a further subsidiary aspect, the system further comprises means for detecting a demand for hot water.

This is of particular advantage when employed in tandem with the hot water pumping means, in that it allows for both the purging of the line and its replenishment with hot water to be triggered by the demand. In a further subsidiary aspect, the system further comprises means for detecting the absence of cooled water in said water line.

This is of particular advantage in that it provides a means for switching from purging to replenishing operations.

In a further subsidiary aspect said means for detecting the absence of cooled water in said water line is an air detector.

Advantageously, this refinement allows for precision in switching from purging to pumping, in that it enables the system to detect when all cooled water has been removed from the pipe, which is when the pipe is empty.

In a still further subsidiary aspect, the system further comprises a thermostat placed in said water line and means for interpreting said thermostatic signal, so that if the temperature of the water present in said water line is above a defined threshold, the system supplies water from the hot water tank in a known manner.

This is advantageous in that the incorporation of the above feature ensures that the purging and pumping system does not operate when it is not needed - i.e. when the water is hot enough already. Such an operation is advantageous, not only because it stops any time delay which might occur between a demand signal and the provision of hot water precipitated by the employment of the system, but also because it saves energy.

In a still further subsidiary aspect, the system further incorporates a timer placed in said water line and means for interpreting said timer signal, so that if the duration that water is present in said water line is below a defined threshold, the system supplies water from the hot water tank in a known manner.

This is advantageous in that the incorporation of the above feature ensures that the purging and pumping system does not operate when it is not needed - i.e. when the water is hot enough already. Here, it is predicted, rather than actual temperature which is relied upon. Such an operation is advantageous, not only because it stops any time delay which might occur between a demand signal and the provision of hot water precipitated by the employment of the system, but also because it saves energy. In a still further subsidiary aspect, the system further incorporates one or more manifolds into which a plurality of hot water lines run.

The incorporation of manifolds allows for the system to govern a multiplicity of lines - for example, the entire hot water system in a house or office.

In a third broad, independent aspect, the invention comprises a method of saving water comprising the steps of: detecting a demand for hot water from a water line; pumping water to the cold water tank; then when an absence of water is detected in said water line pumping water from the hot water tank in order to meet the demand.

These and other objects and advantages of the present invention will no doubt become apparent to those skilled in the art after having read the following description of the preferred embodiments illustrated in several figures of the drawing.

Brief description of the drawings

The invention will be described with reference to the accompanying drawings in which:

Figure 1 is a two - part flow chart illustrating a preferred embodiment of the invention. Figure 2 is a schematic drawing of a water saving system, with a pump in the first position. Figure 3 is a schematic drawing of a water saving system, with a pump in a second position.

Figure 4 is a schematic drawing of a water saving system, with a manifold. Figure 5 is a schematic drawing of a water saving system.

Figure 6 shows a plan of a further embodiment of a water saving system.

Detailed Description of the preferred embodiments

Figure 1 shows a preferred embodiment of the invention. It is illustrative of the elements which may comprise a preferred embodiment or embodiments of the invention. In particular, note the controller box, the flow meter switch, the timer-switch override and the thermostatic mixer including one way valve. This system of figure 1 incorporates two separate pumps A and B. Pump B is considerably less powerful than pump A. Pump B is selected to be able to drive hot water to a tap and to overcome any obstacle such as an air bubble. Pump A is selected to be able to draw cooled hot water up to the cold water header tank and overcome cavitation problems which may arise in the suction process.

In the case of a power failure or of the failure of a pump, the system optionally incorporates one or more by-passes allowing the ordinary water distribution system to by- pass the system.

Figure 2 shows an embodiment of a water saving system 10, with a pump 12 in the first position. The water saver comprises a hot water tank such as hot water cylinder 14, connected to a hot water outlet 16, which in this case is a tap (or "faucet") by a water line 18. The outlet need not be a tap - it could be a domestic appliance such as a clothes or dish-washer, or any known water demand source.

The hot water line 18 features gating means 124, temperature sensing means 110, which is a thermostat, temperature predicting means 112, which is a timer, a sensor for detecting air 114, a pump 12 and a demand sensor 116. The pump 12 is bi-directional or incorporates two separate pumps and as such is placed of necessity at the junction between the hot water line 18 and the purge line 118. A bi-directional pump is formed by providing means to reverse the polarity of the pump which may be part of the system controller.

There is no separate purge line between the taps and the pump so that no modification to the existing plumbing is required between the system and the taps. The pump purges the existing hot water line or lines and draws the cooled hot water through a purge line to the cold water header tank.

The purge line 118 runs from the hot water line 18 to a cold water tank 120. In this embodiment the cold water tank 120 is a header tank feeding the hot water tank 14 via a connecting line 122. In use, upon the opening of hot water outlet 16, demand sensor 116 is alerted. All alerts, communications and signals are made and received using technology known to the skilled reader and appropriate to the task.

The demand sensor 116 is in communication with thermostat 1 10 and timer 112. If the thermostat 110 indicates that the temperature of the water already in line 18 is too low, or if the timer 112 indicates that the water has been in the line 18 for too long a time, and therefore is likely to be cold and/or stagnant, an actuation signal will be sent to the pump 12. Upon reception of this signal, the pump 12 is actuated, pumping in a purging direction 12a, that is so as to direct water down the purging line 118.

Clearly, there are some embodiments which may function with either the timer or the thermostat, rather than both as here.

Alternatively, if thermostat and timer conditions are satisfied - i.e. the water is of a sufficient temperature and has not been standing in the line 18 for a sufficiently long time, then the pump 12 will not be actuated and the water flow will proceed as normal.

The pump 12 removes the cooled water from the water line 18 and up the purge line to the cold water tank 120. In order to stop the pump 12 from pumping already hot water from the hot water tank 14 to the cold water tank 120, gating means 124 is employed.

In- figure 3, when the cooled water is removed from water line 18, the air detector 114 will sense this. It will communicate a signal to the pump 12 to stop pumping in a purging direction 12a and change configuration so that it pumps in a hot water supplying direction 12b, as shown at figure 3.

In this embodiment, the demand sensor 116 has means to detect the reaching of water to the demand site 16. On detecting the flow of water, pumping will cease, and normal flow will proceed. In other embodiments, pumping may continue until demand ceases, which in this case would be indicated by the closing of the hot water outlet 16 and sensed by the demand sensor 16. In embodiments featuring a timer 112, as here, this lack of the demand will be communicated to it by the demand sensor 16 and will serve to reset it. Figure 4 shows a further embodiment of the invention. This version is available in a single box 32 for fitting into domestic or commercial premises. It has a manifold 34 in order that a multiplicity of demand sites may be served with fast, fresh and hot water.

The pump 12 may be a single pump. Alternatively it may be two pumps, one to perform the purging function and one to perform the hot water supplying function, governed by switching means to switch between the two pumps. The relative sizes of the pumps and the calibre of their pumping ability may also vary. In embodiments where the hot water line 18 is pressurised, it need only fulfil the purging function, and can simply let hot water run from the tank to the demand site, without having to pump it at speed. The pump or pumps may be connected to energising means, such as a fuel cell, or mains electricity.

The cold water tank 120, to which the purge line 118 runs, need not be a hot water header tank. It could be the cold water tank of a water system. Filtration means (not shown) could ensure that the water is of a suitable purity before being introduced into the cold water system. These could advantageously be placed in the purge line 118, the cold water tank 120, or the cold water line itself, (not shown)

Alternatively, the air detector 114 can be any device for detecting the absence of water known to the man skilled in the art.

Figure 5 shows the invention in a further broad independent aspect. This version would be used in any system where a hand basin and toilet is fitted, such as in a cloakroom or a bathroom. It saves a cistern - full of water at each usage by replacing a toilet's mains cold water supply with cooled water lying in existing hot water lines. In the embodiment shown 50 a hot water line 52 supplies a hand basin 54 via a tap 56, although clearly the basin 54 and tap 56 combination could be any well known demand source. A purge line 58 runs from the hot water line 52 to a toilet cistern 510, which has a stopcock 518, although this also may be any known demand source. This is also served by a cold water line 512.

In use, a demand is satiated at hand basin 54. This leaves a quantity of water in the hot water line 52. When the hot water's temperature drops below a pre-defined level, this is made available to the toilet cistern 510. This availability will be facilitated by closure of a first thermostatically responsive valve 514 at the cold water line 512 and the opening of a second thermostatically responsive valve 516 at the hot water line 52. When the toilet cistern 510 communicates a demand to the system, the cooled hot water will flow from the hot water line 52 down the purge line 58 to the toilet cistern 510.

Figure 6 shows a water saving system generally referenced 60. This kind of system may be boxed and fitted into existing systems with minimal modifications. There are provided three water lines 61, 62 and 63 which lead to a plurality of hot water outlets such as the tap (not shown) of a kitchen sink. A pressure switch 64 in communication with the water lines reacts to fluctuations in pressure. For example, if a tap of water line 61 is opened, a pressure drop would be detected by pressure switch 64. A controller is provided so that when a pressure drop is detected by pressure switch 64 as a consequence of the opening of a tap of water line 61, the controller would cause the suction pump 65 to draw cooled hot water present in the water line up through water line sections 66, 67 and 68 back to a header tank 69.

The controller (not shown in the Figure) following the detection of a drop of pressure corresponding to the opening of water line 61, would cause the pressure switch to close solenoid valve 70 and to open solenoid valve 71. Furthermore, the controller would cause the closure of electronic flow switch 72 and would open electronic flow switch 73. Thereby, the controller may instruct the operation of pump 65 in order to purge the cooled hot water back to the header tank.

When pump A has fully purged the cooled hot water in the water line and air has replaced the water, the controller causes the electronic flow switch 73 to close. The normally closed solenoid valve 71 switches off and the solenoid valve 64 is switched to its open configuration. At which point the controller organises the switching off of pump 65 and the switching on thereafter of pump 74 in order to send hot water direct from the hot water cylinder (or other appropriate source) via a thermostatic mixer valve 75 and the manifold 76 to the above mentioned opened hot water tap located on water line 61. Between mixer 75 and respectively the hot water cylinder 77 and the header tank 69 there are provided a hot supply 78 in communication with the hot water cylinder and a cold supply 79 in communication with the header tanks by a cold supply line 80. A typical overflow/return/expansion pipe is provided between the cylinder and the header tank 69. an S-flange 82 is fitted to the top of a hot water cylinder in order to ensure that hot water is drawn from the cylinder and not from the overflow/return/expansion pipe which extends from the cylinder to the header tank. Filters 83 and 84 are provided. Optionally a water meter 85 is provided to inform a user of the system of the amount of water saved by the system.

Instead of the pressure switch, the invention envisages employing a flow meter or any other appropriate means of detecting flow. Two on/off valves may be provided such as those referenced 86 and 87. A gate valve 88 may be provided in the cold supply as indicated in the figure.

At least the following advantages may be achieved by the system:

• Tens of thousands of litres per year may be saved per household.

• The system allows the saving of cooled hot water lying overnight in hot tap pipelines from being wasted down the plug-hole whilst waiting for hot water to arrive at that tap.

• It may also be used to save cooled water which on average cools from hot to cold in a period of between 20 to 30 minutes.

• It allows the cooled or cold hot water to be sucked back up the tap's own existing pipeline which is then returned to an existing header tank.

• Little or no extra pipelines are required.

• It may be used to prevent cold water being sent to appliances such as clothes washing machines which demand hot water.

• A separate part of the system may also allow for toilet cisterns to save several litres of water per usage by employing the system to replenish the cistern with the cooled hot water that is lying in an adjacent hot water pipe which would otherwise be wasted down the plughole of the basin when washing the user's hands. • The system may be readily retrofitted by installing a box housing each of the components discussed above with only external snap-on fittings to be connected to plumbing. There would therefore be applications for both new and old houses.

The following specific equipment may be employed:

• A water pump to lift cooled hot water 10 to 15 feet through hot water pipelines, and then put it up a further 10 to 15 feet. This pump may be operated by a pressure switch activated when a hot water tap is opened.

• A water pump to send hot water down to an open tap at 0.6 litres per second.

• Two flow meters, i.e. one for each pump. These may be fitted "in-line" or incorporated within the two pumps. Wireless thermo-temperature sensors may also be fitted at appropriate locations. The above pressure switch starts the suction pump when a first hot water tap is opened. The pump then purges the cooled hot water from that line.

• The system may incorporate a control system which detects when all cooled hot water has been purged from the line (i.e. air has arrived at it). The system then stops the suction pump and starts the hot water returning pump to send only hot water to the line. The system may also sense when a second tap is opened whilst the hot water returning pump is already in use. In this mode of operation the pump is temporarily switched off for a few seconds in order to allow the suction pump to purge the cooled hot water lying in the pipeline to the second tap and then the hot water returning pump is instantly re-started.

• A thermostatic mixing valve may be set at an appropriate temperature such as 47° Celsius in association with the hot water returning pump to eliminate scalding water being sent to hot water taps. This feature may be particularly attractive in installations employing so-called ACA boilers. • One or two manifolds may be used.

• A header tank with a ball-cock may be needed where existing "flow-return" or "gas/electric instant water heaters" are fitted.

• Electronic one-way valves/thermostats (for use only with "cistern" aspect).

• A ventilated toughened plastic box may be employed to house the main parts of the system.

Claims

1. A water saving system comprising a pump operatively connected to a water line leading to a hot water outlet; means for detecting a demand of hot water at said hot water outlet;

5 means for triggering the operation of said pump in response to the detection of said hot water demand; whereby said pump draws water in said water line towards a cold water storage tank such that the water line is purged; means for detecting the arrival of air at a point of said water line; means for switching off said pump in response to said arrival; said pump or an additional pump being operatively connected to said water line leading to a

W hot water outlet; and means for switching on said pump or an additional pump following said arrival in order to refill said water line with hot water; whereby hot water is delivered at said hot water outlet.

2. A system according to claim 1, wherein said means for detecting a demand for hot 15 water incorporate a pressure switch.

3. A system according to either of the preceding claims, wherein said means for detecting a demand for hot water incorporate a flow meter.

20 4. A system according to any of the preceding claims, wherein said means for detecting the arrival of air incorporates a pressure switch.

5. A system according to any of the preceding claims, wherein said means for detecting the arrival of air incorporates a flow meter.

25

6. A system according to any of the preceding claims, wherein a thermostatic mixing valve is provided in association with said additional pump.

7. A system according to any of the preceding claims, wherein said pump is configured to 30 draw water from said water line to said cold water tank and said additional pump is configured and of relatively lower power than said pump to refill said water line with hot water.

8. A system according to any of the preceding claims, further comprising a thermostat placed in said water line and means for interpreting said thermostatic signal, so that if the temperature of the water present in said water line is above a defined threshold, the system supplies water from the hot water tank in a known manner.

9. A system according to any of the preceding claims, further incorporating a timer placed in said water line and means for interpreting said timer signal, so that if the duration that water is present in said water line is below a defined threshold, the system supplies water from the hot water tank in a known manner.

10. A system according to any of the preceding claims, incorporating one or more manifolds into which a plurality of hot water lines run.

1 1. A system according to any of the preceding claims, wherein said cold water tank is a sanitary unit's cistern.

12. A method of saving water comprising the steps of: detecting a demand for hot water from a water line; pumping water to the cold water tank; then when an absence of water is detected in said water line pumping water from the hot water tank in order to meet the demand.

13. Apparatus for saving water substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying text and/or drawings.