NZ542945A - Water storage system - Google Patents

Abstract

A water storage system comprises a number of pre-formed modular water tanks which are inter-connected to allow water to flow between them. The system also includes a pump and controls. The tanks of the system are shallow relative to their width

Description

54294 5 *10049831230* Patents Form No. 5 Our Ref: MH505664 Patents Act 1953 COMPLETE SPECIFICATION WATER STORAGE SYSTEM We, RINKER AUSTRALIA PTY LIMITED, a body corporate organised under the laws of Australia of Level 8, Tower B, 799 Pacific Highway, Chatswood NSW 2067, Australia hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: PT05A4503295 300476032_1 (Followed by page 1A) i 1 - - lA- WATER STORAGE SYSTEM The present invention relates to a water storage system that can particularly be used to store water below ground.

S Conservation and sensible use of water is very important in drought affected areas. Large cylindrical water tanka to collect rainwater made of corrugated iron, concrete or plastic are commonplace on many rural properties and some 10 metropolitan properties. The water collected by the tank cam be used for irrigation, washing, general household use and drinking.

Xn areas of limited space it may not be possible to 15 install a water tank of the type described above.

Innovative solutions are required some of which have involved installing water tanks within a roof cavity of a building. The drawbacks with such tanks is that they are limited in size owing to the weight capacity of the roof 20 battens. Furthermore, any pumps connected to the tanks are usually noisy and distracting to occupants of the building.

Other solutions include creating a tank in a hole in the 25 ground by casting concrete in formwork in-situ. Such water tanks are expensive and laborious to create as they are often of varying irregular sizes. They are also difficult and expensive to maintain and the nature of construction can sometimes cause leaks, particularly where 30 there has been ground movement.

A simpler and more cost effective water storage system is therefore required.

It is an object of the present invention to provide an improved water storage system, or to at least provide the public with a useful choice.

SUMMARY OP THE INVENTION According to one aspect of the present invention there is provided a water storage system comprising a plurality of preformed modular water tanks each tank having a cover, at least one water inlet and at least one water outlet wherein the tanks are interconnected to allow water to flow therebetween and the tanks are substantially shallow relative to their width; and a pump for pumping water to and/or from the tank, the pump being controlled by controls.

The height of the tank is preferably between 30% and 80% of the width of the tank.

The water tank has a height that is preferably 40% to 60% of the width. The system preferably includes multiple modular tanks and more preferably four tanks arranged in a square. The tanks are preferably made of concrete or part concrete and are substantially rectangular or square in plan view. One corner of each tank may be mitred such that the mitred corners can be arranged in the square arrangement to all face the centre and thereby form a space defining a pump area. In this case the pump is preferably installed in the pump area in a pump well where it is immersed in water.

In another arrangement none of the tanks7 corners are mitred but instead inter-fit modularly with each other. In this case the pump is installed inside one of the concrete tanks where it is immersed in the water held by the concrete tank.

Two or more tanks may be interconnected together and/or to the pump well to allow water to flow therebetween by weirs and/or balance pipes.

Each tank may have a floor inclined towards the centre of the tank for collecting sediment and concentrating it at the centre.

Weirs and/or balance pipes connecting adjacent tanks and the pump area are typically located above the dead zone and preferably in the main water feed zone.

INTELLECTUAL PROPERTY OFFICE OF N.2. -1 FEB 2007 J?£C£IVPD The level indicators are preferably limit switches connected to the control unit to communicate therewith. Where all tanks are interconnected in series to the 5 adjacent tank and the first tank is interconnected to the pump area, the indicators are located in the pump area.

Preferably, where the tanks are connected in series, the collected water inlet is located in the tank furthest from 10 the pump area. The pump area preferably includes the pump, and a backflow prevention valve connected to mains water supply. The pump area further preferably includes filters such as an ultraviolet purification device. The filters can be located in or above the pump area or in or 15 above a tank.

The controls may be located below ground or above ground.

Access hatches with covers are preferably provided in the 20 cover of the tank, and typically at the centre of the tank. All access hatches and inlet and outlet ports are preferably air sealed.

Conduits for the transfer of water or electricity are 25 preferably installed in between the tanks. Specifically, the conduits carry water pumped from the water tank, carry water pumped from the mains water to the tank and carry wiring from electrical mains and controls to the pump area.

The pre-formed tank is preferably relatively shallow for its footprint. For a tank having a footprint or area of 2.3m x 2.3m the internal depth of the tank is not more than 3000mm and preferably about 800mm.

The tanks may be formed of pre-cast concrete or formed from a combination of concrete and plastic. In the latter the tank is preferably a plastic tub having side walls of precast concrete or a plastic lining cast into a concrete tank shell.

In accordance with another aspect the present invention also provides a water storage system comprising a plurality of pre-formed modular water tanks, each water tank having a cover, at least one water inlet and at least one water outlet, the tanks being interconnected, a pump for pumping water to and from the tanks, the pump being controlled by controls, wherein the height of each tank is between 30% and 80% of the width of each tank.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is described further by way of example with reference to the accompanying drawings of which: 2 0 Figure 1 is a plan view of an installed water storage system in accordance with an embodiment of the present invention; Figure 2 is a sectional view of the water storage system of Figure 1 taken at section A-A; Figure 3 is a side sectional view of another embodiment of a water storage system; Figure 4 is an isometric view of an embodiment of the water storage system installed below ground; and Figure 5 is an isometric view of another embodiment of the water storage system installed below a structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The present water storage system will be described by reference to the drawings which illustrate water storage 5 systems located underground or above ground. While suitable for installation below ground level, the water storage system may be mounted above ground. In particular, the water storage system is intended to provide a compact system that is space saving and can be 10 installed in spaces below or above ground.

An underground water storage system 10 is illustrated in the drawings. The water storage system 10 includes modular pre-formed concrete or part concrete tanks 12 that 15 are simple to install and maintain. Each tank 12 has a tank roof 13 that encloses the interior of the tank and prevents the ingress of debris, dirt, insects, etc into the tank. A pump area defined by a pump well 14 contains a pump (not shown) immersed in water in the well 14. 20 Controls (not shown) monitor and regulate the water levels in the tanks.

The present tanks are simple to install and maintain because of their modular nature and their relatively 25 shallow depth compared to their width. So that the system can be installed in space saving places, which are usually found under buildings or under outdoor structures, the modular tanks have been designed to make use of almost any shaped space and requiring only a minimum amount of ground 3 0 excavation, if any.

The tanks have a small height to width ratio wherein the height is approximately 30% to 80% of the size of the maximum width or diameter of the tank. Put in terms of 35 ratios, the height to width ratio of the tanks is between 1:3.3 and 1:1.25. Preferably the height to width ratio is between 1:2.5 and 1:1.6 (ie. the height is 40% to 60% of the width). This small height: width ratio defines a squat water tank that can be installed with minimum complications and with little preparation. In some cases the water tank system can be retro-fitted below existing structures.

While four water tanks 12 are illustrated in Figures 1, 2 and 4 it is understood that the water storage system may operate with only one tank as illustrated in Figure 5. Similarly, there may be a greater number of tanks than four. This will largely be dictated by the capacity of water storage required and the area available for installation. To make efficient use of space the tanks need not necessarily be arranged in a square but may be arranged in a line or an "L" shape, etc, using as many or as little tanks required.

Figure 1 illustrates the four water tanks 12 arranged in a square tank arrangement. The tanks themselves are rectangular and substantially square. One corner of each tank is mitred such that when all four mitred edges from each of the tanks 12 are arranged to face the centre, a space 16 is formed. The pump well 14 is mounted in the central space 16 and therefore has direct access to each of the four tanks. Where more than four tanks are used the pump well is positioned at a location closest to all tanks. Water and electrical conduits may need to be extended.

In another embodiment of the invention (not shown) the square tanks do not have any mitred edges such that the pump space 16 of the embodiments of Figures 1 and 2 is not formed and instead the four tanks meet closer at the center. In this embodiment the pump is located inside one of the tanks and is immersed in the water of that tank and from there pumps water between the other tanks and/or to drainage.

In the illustration of Figure 2 and Figure 4 the water system is illustrated mounted below a concrete sleds 22 of a garage floor. In this embodiment the garage floor is an 5 in-situ reinforced concrete slab of about 100mm. The concrete slab is poured after installation of the water storage system and directly on top of the system securely embedding the tanks. Metal trusses 36 (Figure 3) in the tank roof 13 reinforce the roof and assist in stabilizing 10 the poured concrete slab 22 against movement relative to the lid. The tank roof in the present example is 60mm thick pre-cast concrete permanent fonnwork.

Each tank roof 13 has an access hatch 24 generally located 15 above the centre of the tank. Provision for corresponding access is made in the garage floor when pouring the slab 22. Hence, direct access is provided to each tank through the slab floor 22 and through the tank roof 13. An access hatch 24 is also provided above the centre of the water 20 storage system for accessing the pump well 14, if this design is used. The access hatches are sealed with manhole covers 24 which are preferably made of cast iron and seal the holes gas tight. In the present example the hatches are round 600mm in diameter, but they could be rectangular 25 or square.

As discussed the tanks 12 are of relative shallow construction when compared to the surface area occupied by the tank, namely the footprint. In the sectional side 30 view illustrated in Figure 2 the tanks 12 can be seen as having a relatively shallow depth compared to their footprint. The benefits derived from this tank construction is that the tanks can be installed below ground into a shallow dug recess. This makes the water 35 storage system ideal for storing below, for example, a garage floor of a house or an outdoor structure or living area such as a timber deck. In particular, because only a shallow recess is required to be dug the water storage system may be installed in areas having hard clay ground or shallow rock.

Owing to its shallow, compact and modular nature the present water storage system is directed to compactly occupy out of the way spaces, which can generally be found or dug under interior or exterior floors. Figures 4 and 5 illustrate two different types of installation. Figure 4 10 illustrates the water storage system installed underground under the garage 60 of a building.

Figure 5 illustrates the water storage system 10 mounted above ground but below an outdoor decking area 65 wherein 15 the concrete walls 66 are not entirely mounted below ground but may exposed above ground.

Furthermore, the large footprint and shallow depth allows significant storm water attenuation volumes to be released 20 slowly into drains at a shallow outlet depth.

In the illustrations shown, the tanks are approximately 800mm deep internally and have a surface area, or footprint, of 2.3m x 2.3m. This depth has been selected 25 for practical entry of a person to carry out cleaning/maintenance and to facilitate general installation of the tank. During the life of the water storage system, the tanks can be drained and entered by a person to repair or replace parts including balance pipes, 30 seals and the like.

The volume of the modular tank holds approximately 3 000 to 4000 litres. It is envisaged that two tank sizes will be provided: a small size that holds 3000 litres and a large 35 size that holds 4000 litres, so that options will be available in selecting volumes according to multiples of 3000 and 4000 litres.

The particular 2. 3m x 2. 3m footprint dimension has been selected according to the size of a standard double garage floor and the fact that four tanks may be arranged in a 5 square underneath the garage floor. These dimensions also suit the grid centres of polystyrene waffle pod systems, known for constructing house foundations. The size of the modules also ensures that they are of a mass and size suitable for road transportation and handling by small to 10 medium cranes during installation.

Placing the system underneath a building or other structure firstly enables it to be easily accessed for maintenance, and secondly moves it away from outdoors, or 15 other areas, where the outdoor space could be put to other uses. Of course, if desired the system may be placed underground or aboveground outdoors, but the compact and modular nature of the system gives a user more options.

The tanks can vary in size depending on location and application from an envisaged minimum of lm x In to a maximum of 20m x 20m. To suit transportation and handling practicalities, the tanks are more likely to have a footprint of between lm x lm and 5m x 5m, and preferably 25 2.3m x 2.3m. Moreover, the tanks need not be square but can be rectangular or any other geometric shape, as is practical.

While the depth of a 2.3m x 2.3m tank is preferably 800mm 3 0 it is possible within the concept of the water storage system for the depth to be as high as 3000mm for a tank having a greater footprint. The depth will obviously be a function of the footprint of the tank. 3 5 The pre-formed tanks are designed in standard sizes and of relatively standard dimensions such that the tanks become modular. This makes the water storage system easier to design according to the required application parameters for instance, the water capacity required and footprint available. Additionally, modular cells of the same size or a set of standard sizes are easier to manufacture and 5 stack. It is preferred to keep the tanks below a specific volume capacity such that the tanks are small enough to be easily transported and handled and evenly bedded in the ground.

The tanks illustrated in Figures 1 and 2 are pre-cast tanks made entirely of concrete. Figure 3 illustrates another embodiment where the pre-formed tank 12 is only partly made of concrete. A plastic tub 50 forms the tank structure and is supported with precast concrete side walls 52. This embodiment is ideally installed on a sand base and can accommodate differential movement of the ground. The pre-formed concrete and part concrete tanks are cast in a controlled factory environment to ensure quality and a watertight tank.

In yet another embodiment (not illustrated) the tank comprises a pre-cast concrete base and wall having the inner surface of the tank lined with plastic that is cast into the concrete to provide an internal plastic lining.

This version improves the strength and rigidity of a tank over the version of Figure 3 while confidently maintaining a sealed inner surface to prevent any seepage of water through the concrete walls. 3 0 In the embodiment illustrated in Figures 1 to 4, the tanks 12 are bedded in a shallow dugout in the ground. As illustrated in Figure 2 a strip of concrete building foundation 18 encloses the area occupied by the water storage system 10. The foundation 18 provides support for the building 45 and provides lateral support for tanks 12 which can be placed firmly against the foundation.

To ensure stability sand fill can be packed in the voids 20 around the tanks, between each tank 12 and around the central pump well 14. Alternatively, an air void may be created between the tanks and around the pump well 14. Conduits for electrical wiring and plumbing can be provided in the voids between the tanks. The voids can be set at a fixed distance by creating the permanent fonnwork of the tank roof 13 to overhang past the side of the tank 12 by a distsince equal to the width of the void.

Overall, the modular pre-cast construction of the water storage system provides for simple installation with the only preparation required being the digging of a shallow recess, if required, ensuring adequate bearing capacity of 15 the underlying soil, and providing a level bedding.

Two or more tanks and the pump well can be interconnected by weirs and/or balance pipes 26. Figure 1 illustrates all four tanks 12 interconnected to the tank adjacent to 20 it by a balance pipe 26. Pump well 14 is also shown connected to one of the tanks by balance pipe 2 6, but can be directly connected to all four tanks, or totally immersed in one tank. Accordingly, all four tanks are connected to act as one large water storing facility of 25 varying shapes and varying volumes depending on the number of tank modules chosen and depending on the shape chosen in which to lay the tanks.

The tanks may alternatively be de-connected such that, for 30 example one tank is only connected to one other tank.

This is useful where separate storage areas are required. For example rain water could be collected and stored in one storage area comprising two tanks while it is envisaged that grey water could be stored in the other 35 storage area. Grey water is used water collected from basins, washing machines, and the like, for re-use. Water from the tanks would then be re-directed according to which tank the water is pumped from. For instance, water from the rainwater tank could be pumped into the house for drinking or bathing purposes while grey water could be pumped to the garden or to toilet cisterns.

In another embodiment the tanks could be interconnected in a series sequence so as to form a path through which the collected water flows from its point of entry in one tank through each of the four tanks to end up in the central pump well 14. It is envisaged that by creating such a path the collected water will be relatively cleaned of sediments and other deposits as it travels through the tanks. The heavier particles in the water will settle to the bottom of each tank such that by the time the water enters the pump well it is relatively clean. At this point the water may also be filtered as it is pumped from the pump well.

The controls (not shown) control incoming water, outgoing water pumped from the tanks and monitors water levels. The controls may be located in any of the voids 20 below ground or in a separate control panel above ground. The controls may also include a pressure device (not shown) connected to building plumbing and which detects a drop in pressure in the plumbing line caused by a water valve being opened. Once the drop is detected, the controls activate the pump to start up and pump water from the tanks and into the building plumbing.

The pump well 14 includes the water immersed pump to pump water from the storage tanks 12 into the building's plumbing. The water storage system 10 is also tapped into the water mains. If the water level in the tanks 12 falls below a pre-determined level water from the pressurised water mains is released to the tanks. The tanks can therefore be used as a building's primary water supply. With access to mains water even if the amount of collected rainwater drops, users can rest assured that mains water will keep the tanks continuously supplied with water.

Figure 4 shows an alternative arrangement whereby a 5 switching controller 68 detects low water levels in the tank and switches to supply mains water to the building rather than the collected tank water.

Pump well 14 also includes a backflow prevention valve 10 (not shown) on the mains water line to prevent the backflow of stored water into the mains. A UV light water purification device and/or filters may be installed (not shown) in the pump well 14, in a tank or downstream of the tanks to improve water quality as it is pumped from the 15 tanks into the building plumbing.

The pump well 14 also includes water level indicators 55, 56, and specifically limit switches, that identify whether the water level is above or below set levels. This 20 information is processed by the controls for monitoring the water level in the tank and initiating appropriate action.

In the embodiment where all four tanks of the storage 25 system 10 are interconnected to each other and to the pump well 14, the level indicators are located in the pump well. In the embodiment where not all tanks are interconnected, level indicators will need to be provided in the tanks themselves to monitor the water in each tank 3 0 or each set of tanks, which will be different if the tanks are separated.

Each tank can be divided into a number of horizontal zones defined by the water level according to outlet positions 35 and monitored by the indicators. As shown in Figure 2 and beginning from the bottom, shallowest end of the tank the zones are: dead zone 30; mains water feed zone 31; rainwater zone 32; storm water zone 33 and an air zone 34 at the top of the tank.

An air pocket is always maintained at the top of the tank 5 at the air zone 34. An overflow outlet 40 defines the bottom of the air zone and the top of the storm water zone and ensures that if the water level reaches the air zone it will be discharged through the overflow outlet 40 without climbing any higher. The overflow outlet is a 10 pipe having a typical storm water diameter of approximately 90-100mm to allow for fast discharge of water into storm water drains when the water level in the tanks becomes too high.

As illustrated in Figures 4 and 5 collected rainwater is collected from the roof 72 of a building and carried to the water storage system 10 by downpipes 73. Two stage filters 75 near the bottom of the downpipes 73 filter first leaves then particles greater than 0.5mm before 2 0 supplying water to the tank system. Grey water is collected from inside the building and carried to the system 10 by internal plumbing. Collected rainwater and/or grey water enters the water tanks through inlet pipe 42 at the air zone 34. Each tank 12 may be provided 25 with its own inlet pipe 42, however if the tanks all inter-communicate only one inlet pipe 42 to the system is required, although each tank will have its own inlet and outlet. The inlet pipe 42 may also be provided at the pump well.

At the storm water zone 33 the water level is at a high. To keep the water level below or around the storm water zone 33 a slow storm water outlet 44 defining the bottom of the storm water zone slowly releases water to storm 35 water drains 70 (Figures 4 and 5). The intention of the slow release of water is to discharge excess water through to storm water drains at a slow flow rate so as to prevent burdening storm water drains with a high flow rate in significant storm events. Slow release of water from the storm water zone 33 allows the storm water drains 70 to be reduced in size and used efficiently.

Slow release of water from the storm water zone 33 is effected by the storm water slow outlet pipe 44 having a smaller diameter than the standard storm water drain pipe diameter of 90-100mm. It is envisaged that slow outlet 44 10 will have a pipe of a diameter of approximately 10mm to 50mm, and preferably about 25mm, to decrease the outgoing flow rate.

The optimum water level in the water tanks is at just 15 below storm water outlet 44, that is, at the top of the rainwater zone 32. Below the rainwater zone 32 the collected water level is considered to be getting low and water will need to be drawn into the storage system 10 from water mains.

A low level indicator 55 in the form of a limit switch at the bottom of the mains water feed zone 31 signals when the water level drops to a point where the tanks require replenishing. At this stage water is drawn into the pump 25 well from a mains water inlet 48.

Mains water inlet 4 8 is located anywhere above the dead zone 30 and in the drawings the mains water inlet 48 is illustrated as entering the storage system at the air zone 30 34. Accordingly, if the level of collected rainwater falls below the rainwater zone and nears the bottom of the mains water feed zone, the low level indicator 55 will signal the drop in water level to the controls and water from the pressurised mains water will be released into the 35 pump well or tanks.

The level at which mains water begins to feed into the system can be varied according to design and is set by selecting the position of the low level indicator 55. The level at which the mains stops feeding water into the 5 system is set by selecting the position of a high level indicator 56, which in the embodiment shown defines the top of the mains water feed zone 31. When high level indicator 56 detects that the water levels has reached the indicator, the controls close the mains valve and stop the 10 supply of water into the system. The mains valve has a backflush prevention valve to prevent stored water entering the mains.

While in Figure 2 low and high level indicators are marked 15 in the tanks, it is understood that the indicators can typically be located in the pump well 14. The indicators may comprise any mechanical and/or electrical construction capable of detecting water levels and communicating the detection to the controls.

The balance pipes and weirs interconnecting two or more tanks are provided at the bottom of the mains water feed zone 31 so that water can flow between tanks even at a low level.

Sediment and other suspended solids collect at the bottom of the tank in the dead zone and are prevented from migrating between tanks by positioning the weirs and balance pipes above the dead zone. The tank bottom 28 may 30 be cast to slope towards the centre of the tank so that the majority of the solids collect at the centre, which is easily accessed for cleaning through access hatches 24 located directly above the centre of the tank.

Inlet and outlet pipes can be pre-cast into the concrete walls. Conduits can also be pre-cast in the concrete walls to provide for electrical wiring to power the control unit components. Alternatively, and as mentioned above, conduits and pipes can be provided in the voids 20 between the tanks 12.

The present water storage system provides an attractive means for collecting and storing water, particularly in confined spaces. The system may be mounted underground beneath a concrete slab forming the floor of a house, a garage, an apartment block, an office block, or above ground in a space saving location. The identical, modular pre-cast tanks allows the water storage system to be designed according to required water capacity, building the system from a minimum of one tank to any multiple number of tanks arranged in any shape.

The pre-formed modular shallow tanks, although suitable for mounting below ground, can also be mounted above ground wherein the tanks form a supporting surface for another structure. For example, the tanks may be installed above ground as a support to a walkway or deck area as illustrated in Figure 5.

The tanks can also be installed above or below ground along the northern side of a building whereby the tank modules, full of stored water, store heat from the sun during the day and release heat to the building at night.

In the embodiment where the tanks are mounted underground, locating the pump well underground reduces noise transfer from operation of the pump. Immersing the pump in water in the pump well or a tank cools the pump during operation and also contributes to noise dampening.

The access hatches provide ease of cleaning and maintenance of the tanks and pump well. Because the temperature underground is lower than atmospheric temperature or temperature in a roof cavity, there is a lower likelihood of condensation of the water in the tank than with other systems.

Being installed underground or below structures the water storage system allows for maximum yield of water from storms due to the ability to collect water from the entire roof area and effectively drain the water if necessary.

Owing to the shallow construction of the tank deep excavation is not required and a large water surface area in the tanks allows significant attenuation of storm water discharges.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

INTELLECTUAL PROPERTY OFFICE OF N.Z. -1 FEB 2007 .received 19 1. 10 3. 4 . 5. 7. 8.

Claims (1)

1. CLAIMS DEFINING THE INVENTION ABE AS FOLLOWS: A water storage system comprising a plurality of pre-formed modular water tanks each tank having a cover, at least one water inlet and at least one water outlet wherein the tanks are interconnected to allow water to flow therebetween and the tanks are substantially shallow relative to their width; and a pump for pumping water to and/or from the tank, the pump being controlled by controls. The water storage system claimed in any one of the preceding claims, wherein the height of each tank is between 30% and 80% of the width of the tank. The water storage system claimed in claim 2 wherein the height is between 40% and 60% of the width. The water storage system claimed in any one of the preceding claims, wherein the tanks are square. The water storage system claimed in any one of the preceding claims, including four tanks arranged in a square. The water storage system claimed in claim 5, wherein one corner of each tank is mitred such that the mitred corners are located in the centre of the square arrangement to form a space defining a pump area in which the pump is installed. The water storage system claimed in claim 6, wherein the pump is immersed in water in a pump well in the pump area. The water storage system claimed in any one of claims 1 to 5, wherein the pump is located in a tank. 20 10. 5 11. 10 12. 15 13. 14. 20 16. 25 17. 30 18. The water storage system claimed in any one of the preceding claims, wherein the tanks are connected in series. The water storage system claimed in any one of the preceding claims, wherein the tanks have an inclined floor towards their centre for collecting settlement at the centre. The water storage system claimed in any one of the preceding claims, wherein weirs and/or balance pipes connect adjacent tanks. The water storage system claimed in claim 6 or 7, wherein the pump area includes the pump and a back flow prevention valve connected to mains water supply. The water storage system claimed in any one of the preceding claims, including water treatment devices located in a said tank or outside the tanks. The water storage system claimed in claim 13 wherein the treatment device is a water filter located in the pump area. The water storage system claimed in claim 13, wherein the treatment device is an ultraviolet purification device. The water storage system claimed in any one of the preceding claims, wherein the controls are located below ground or above ground. The water storage system claimed in any one the preceding claims, wherein air sealed access hatches are provided in the cover of the tanks. The water storage system claimed in any one of the preceding claims, wherein c ansfer 21 19. 5 20. 10 21. 22. 15 23. 24. 20 25. 26. 25 27. of water and/or electricity are installed between the tanks. The water storage system claimed in any one of the preceding claims, wherein the water tanks are formed from pre-cast concrete. The water storage system claimed in any one of claims 1 to 18, wherein the water tanks are formed from a combination of concrete and plastic, the tanks each including a plastic lining cast into a pre-cast- concrete tank. The water storage system claimed in any one of the preceding claims, wherein each tank has a footprint of between lm x lm and 20m x 20m. The water storage system claimed in claim 21, wherein the footprint is between lm x lm and 5m x 5m. The water storage system claimed in claim 22, wherein the footprint is approximately 2.3m x 2.3m. The water storage system claimed in claim 22 or 23, wherein the internal depth of each tank is not more than 3000mm. The water storage system claimed in claim 22, wherein the internal depth is approximately 800mm. The water storage system claimed in any one of the preceding claims wherein each water tank has a volume of between 3000 and 4000 litres. A water storage system substantially as herein described with reference to the accompanying drawings.