AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Applicant(s): MATHERSON CONSTRUCTION PTY LTD, ACN 087 275 198 Actual Inventor(s): PETER MATHERSON Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade Box Hill Victoria 31.28 Australia Title: WATER STORAGE SYSTEM IN BUILDINGS Divisional Application of: Application No. 2003262222 The following statement is a fill description of this invention, including the best method of performing it known to me/us:- WATER STORAGE SYSTEM IN BUILDINGS CROSS REFERENCE TO RELATED APPLICATIONS 5 This is a divisional application of Application No. 2003262222 which, in turn was Associated with patent application no. 2002952653. The contents of those applications and their specifications are incorporated herein by this cross reference. FIELD OF INVENTION This invention relates to building construction and water collection systems 10 therein. More particularly, this invention relates to building structures with sub-floor water storage systems and methods for constructing them, e.g. for domestic dwellings. BACKGROUND ART The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common 15 general knowledge in the art in Australia. Population pressures and long term climatic conditions, increased irrigation demands and poor water conservation pressures have placed water authorities throughout the world, particularly in drier regions, under increasing pressure to provide users of mains water systems with an adequate supply of potable water. There is 20 increasing demand for systems and devices which better utilise the precious water resources available through the mains water systems and from primary sources such as rain water and run off. In this regard, regulatory regimes governing the use of domestic water tanks have been modified in line with the growing demand for domestic users to trap their own water from rain water sources, such as run off from roofs, driveways, and 25 the like. Moreover, there has been increased developmental activity directed to the utilisation of dirty or grey water sources such as washing water which may be recycled for use in, for example, toilet systems and gardens. However, large water tanks may be considered unsightly from an aesthetic view point and may occupy critical space, particularly on small domestic blocks. Moreover, 2 their supports must be adequately rated for high load bearing thereby often ruling out the option of placing the tank on the roof of a building structure. Another aspect of the prior art relates to the expense of raft slabs which require a high volume of concrete to form the base of a building structure, such as a domestic 5 dwelling, factory or the like. An object of the present invention is to ameliorate one or more of the above mentioned disadvantages or difficulties of the prior art or, at least, to provide a useful alternative thereto. SUMMARY AND DISCLOSURE OF INVENTION 10 According to a first aspect of the invention there is provided a method of constructing a building structure having a water collection system, comprising the steps of: providing a space to be occupied by a concrete slab of the building structure, is positioning a plurality of prc-made water storage tanks on the ground within the space for the concrete slab, installing connecting pipe work enabling water communication between the water storage tanks positioned in the space for the concrete slab, placing form work to define boundaries of the space to be occupied by the 20 concrete slab and so that the positioned water storage tanks and form work define spaces where the concrete slab will form primary building support structures for walls of the building, locating reinforcing within the spaces between the water storage tanks and the form work where the primary building support structures for building walls will be 25 formed, pouring concrete throughout the space within the boundaries defined by the form work and over the water storage tanks so as to form a floor slab of the building structure 3 including reinforced primary support structures for supporting walls of the building structure and having the water tanks incorporated into the concrete slab for storing water therein beneath the floor slab and between the primary building wall support structures. Preferably the water tanks have water therein during the pouring of the concrete 5 slab so as to help resist external pressure loadings. The water tanks are preferably partially filled with water to help them resist collapse during the pouring of the concrete around and over the tanks to form the concrete slab. Preferably the concrete slab extends continuously across the tops of the water tanks to form a slab floor of the building structure and wherein the primary building wall 10 support structures for walls of the building to be erected thereon are defined between the water tanks and outside boundaries of the slab defined by the form work. The water tanks are preferably made of moulded plastics material. The method preferably further comprises the step of connecting the water tanks so as to receive and store rain water from the guttering system of the building structure. 15 According to a second aspect of the invention there is provided a water collection system in a. building structure including a plurality of water tanks in fluid communication with each other and connected to a water source to supply water to the tanks, wherein all the tanks are incorporated into a concrete foundation slab of the building structure as a result of concrete being poured around and over the tanks such that the tanks are 20 permanently positioned within a perimeter of the concrete foundation slab and between reinforced bodies which are integral parts of the concrete slab and which are forming structural supports for walls of the building structure erected thereon, and such that in use the tanks store water below a floor of the building structure formed by the foundation slab. 4 Preferably the water source is a rain water supply which sources the rain water supplied to the tanks from the building structure. The system may include a water level regulation means to maintain the amount of water stored in the plurality of tanks above a predetermined level. The water level regulation means may includes a valve in a line in 5 communication with a mains water supply such that when said water regulation means senses the level of water stored in the plurality of tanks falling below said predetermined level, the valve in the mains water supply line is opened to permit the ingress of water from the mains water supply to return the water level stored in the plurality of tanks to or above said predetermined level. Also the water level regulation means may include a 10 preliminary container located externally of the foundation slab and at substantially the same level as and in communication with the tanks incorporated in the slab, the at least one water source supplying water to the preliminary container and the water level regulation means being responsive to the level of water in the preliminary container. In the preferred water collection system, the water tanks have been positioned on is the ground within a space for the concrete slab, have been connected by pipe work enabling water communication between the water storage tanks, and have been incorporated into the concrete slab by pouring concrete throughout the space within boundaries defined by form work and entirely over the water storage tanks so as to form an integral floor slab of the building structure with the water tanks permanently 20 incorporated into the concrete slab for storing water therein. Also preferably the water tanks were partially filled with water to help them resist collapse during the pouring of the concrete around and over the tanks to form the concrete slab. In one particular preferred aspect, this invention may provide a container or tank forming part of a sub-floor building structure, the container defining a space filled with 25 liquid to a sufficient level to resist the collapsing of the container walls under the 5 pressure of external loads applied to the walls by the remaining sub-floor building structure components or materials. The remaining sub-floor building structure materials or components may form a floor slab. The liquid may be water and the container may be a water storage tank. 5 The water may be supplied from primary sources such as rain water and run off from paved surfaces such as driveways. The water may also be recycled water obtained from grey water sources such as dishwashing machines, clothes washing machines, kitchen sink water and the like. The water may also be sourced from a secondary supplementary source such as mains water. 10 The supplementary mains water outlet may be fed directly into the system without passing through a filtration system. Conversely, the water derived from primary sources may be directed through a filtration system before being admitted to the water tank. The filtration system may be interposed between the primary water source collection area and the water tank. The filtration system may be included in a common i5 pipeline in communication with all of the primary source collection areas. Alternatively, the filtration system may comprise a plurality of different filtration devices specifically adapted to filter out particular contaminating elements which characterise the particular primary source. For example, the filtration system may include one or more filters specifically adapted to remove leaves and other debris (such 20 as by wire mesh) borme by water derived from roof areas and the silt and other sedimentary elements characteristic of ground level run-off may be filtered out using matted fibre or woven fibre filters, as appropriate. The water storage system. may include different water tanks or compartmentalised non-communicating water tanks to manage water from different sources of different 25 quality. For example, the water storage system may include a tank or compartment dedicated to storing water derived from rain water sources and a separate non communicating compartment dedicated to storage of water derived from grey water sources. As the skilled person will appreciate, the water derived from rain water may be more easily treated to obtain water of a potable quality, whereas grey water may be 30 recycled for use in toilet systems and for watering gardens, etc and may therefore be subject to a less stringent treatment regime. 6 Preferably, where a mains water source is available, the water storage system includes a mains outlet control device for regulating the mains water outlet whereby, when the water level achieved from. the primary water sources drops below a predetermined threshold in the tank, the mains outlet control device opens to permit 5 entry of mains water to the system. There are various means for detecting and regulating water levels which will. be familiar to a person skilled in the art and it is merely noted that a float or ballcock device operably connected to a mains outlet valve would be satisfactory for this purpose. The mains outlet control may be located in the tank or may be located external thereto. 10 In a preferred arrangement, the mains outlet control is located in a preliminary tank in direct communication with the tank. Mains water may be fed directly into the preliminary tank. In a particularly preferred arrangement, the water from the primary sources is fed into the preliminary tank via the filtration system located in the preliminary tank. Accordingly, maintenance and repair of the mains outlet control is device and tbe filtration system may be carried out by an operator by reference to the same location. The water tank is typically large in capacity by domestic standards and may range from 5,000 to 20,000 litres for domestic applications and may be much larger in capacity for commercial applications such as for use in farm, office and factory 20 buildings. The water tanks are preferably precast or premoulded and are made in a range of dimensions and configurations corresponding to the variety of different applications. Typically, a domestic water tank according to the invention will be about 5 to 12 metres in width and length and about 100 to 800 mm in height. The tank may be made from a variety of suitable materials such as metal or 25 plastic. Although galvanised metals may be utilised, if metal is required for structural reasons, it is preferred that stainless steel be used to provide corrosion resistance particularly in corrosive environments such as close proximity to sea water. In most applications, however, plastics materials will be adequate in terms of strength 7 requirements and preferred in terms of ease and cost of manufacture, corrosion resistance and transportability. Moreover, as resistance to UV degradation is of no significance in the sub-floor environment, plastics materials will be generally preferred. Polypropylene, optionally strengthened by additional constituents, is particularly 5 preferred. The tank may be of a simple hollow construction with provision for inlet and outlet pipes and optionally air vents. The tank may include inclined external walls. Preferably the external walls are inclined inwardly so that the tank is wider at the base than at its roof. This configuration is particularly preferred where the tank is intended 10 for a load bearing application. The corners and edges of the tank may be angular. However, it is preferred that the corners and edges be curved to provide greater strength and ease of manufacture, such as in a plastic moulding process. The tank may be located in the interstices extending between the building support structures. Preferably, the tank is dimensioned and configured to occupy a substantial i5 volume of the space extending between the building support structures. In doing so, the water filled tank is useful to moderate the temperature of the building by providing a large body of water immediately below the floor. This typically has the effect of averaging out the temperature experienced by the building over a period of weeks and even months. The tank itself is removed from direct exposure to the environment of the 20 building whereby to further moderate the temperature of the water therein. In particular, it is not exposed to direct sunlight, nor is it exposed to frosts and the like where the sub-floor area is enclosed. Preferably, the tank is installed as part of the building process of the building and, preferably, when the foundations of the building are being laid. The tank may be 25 suitably located in the sub-floor cavity of a building supported by a bearer and joist system whereby the tank is located between any one of the following: (a) opposed or adjacent footings of the building; (b) a line of the building's footings and a stump line; or 8 (c) opposed or adjacent stump lines. In a particularly advantageous arrangement, the tank is incorporated into a slab as part of the formwork thereof. The tank is particularly well adapted to form part of the formwork in that the water filled container is resistant to collapsing under load due to 5 the outward pressure of the water contained therein, whereby the tank provides an extremely useful utilisation of the void and reduces the amount of formwork required and the time required to set it up. Therefore, the tank may be placed in position prior to pouring the concrete raft slab, filled with water to strengthen the structure against collapse, the other fonnwork placed in position as appropriate and the concrete poured. 10 Optionally, prior to pouring and positioning of the tank, connecting pipe work between the various water beariiig components of the water storage system may be set in place by minor excavation of the soil at a level lower than the base of the tank. To provide increased load bearing capacity of the tank, the tank may include internal vertical supports. The internal vertical supports may be in the form of solid or 15 hollow blocks, posts or walls. The vertical supports may be in the form of one or more partitions whereby to compartmentalise the tank. Preferably, the vertical supports include archways, apertures or channels at their lower most portions permitting or facilitating communication between the compartments to allow flow of water therethrough. It is preferred that the vertical supports extend to the base of the tank for 20 maximum strength, although in some applications it may be adequate to weld or otherwise affix the vertical supports to the side walls of the tank, whereby to effectively support the roof. The water tank may be connected via water pipe work to all or selected water outlets in the building, such as kitchen, laundry or bathroom facilities. As the water 25 outlets will typically be elevated relative to the water tank, it is generally advantageous to provide a water pump to pump water against gravity to the elevated outlets. In another aspect the invention may provide a method for occupying the space between spaced subfloor building support structures including installing a water tank between said structures. 9 Preferably the method includes the further step of maintaining a minimum water level in the tank to provide resistance to collapsing of the tank walls subjected to external inwardly directed loads. Preferably the method includes the further step of using the tank as formwork to 5 define the support structures during construction of the building. Preferably the method includes the following steps: a) placing the tank in position prior to pouring a concrete raft slab; b) filling the tank partially or fully with water to strengthen the structure against inward collapse; 10 c) optionally placing the other formwork position; and d) pouring the concrete around the external spaces defined by the tank and optionally the other formwork. BRIEF DESCRIPTION OF THE DRAWINGS The invention may be better understood from the drawing of Figure I which 15 shows one possible preferred embodiment, and in which: Figure 1 is a schematic side sectional view of a domestic dwelling according to a first embodiment incorporating a water storage system in which the dwelling is built on a slab. Figure 2 is a schematic side sectional view of a domestic dwelling built on a 20 bearer and joist system incorporating another type of water storage system but not embodying the present invention. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to Figure 1, there is shown domestic dwelling 10 including a water storage system 1L The water storage system i includes a rain water collection 25 arrangement whereby rain water is collected off the roof 11, the rain water running into a gutter 12 and down a downpipe 13. The rain water is then directed to a preliminary 10 treatment tank 20 where the water is passed through a filter 21 and down into the main body of the preliminary tank 20. The water storage system I includes a pair of water tanks 30 and 40 wbich are in com lieatioll with the prel-inary tank 20 and each other by means of subterranean 5 ;-ilecting pipes 31, 41. The water level in each of the preliminary tank 20, and the water tanks 30, 40 is always maintained in equilibrium by operation of the direct comnicration through subterranean pipes 31, 41. The first tank 30 is Co1pantmentalised by partitionls 32 which extend from the base 33 of the tank to the oof 34 Each partition 32 includes an aperture 35 whereby the water is freely 0 comrn-inicable between the different compartments within the tank 30 such that the water level of the tank 30 is the same in each compartment, once equilibrium is achieved. In contrast, the second tank 40 is a hollow non..compartmentalised structure. The second tank 40 has inclined side walls 42, a base 43 and a roof 44. Depending on the i5 load bearing requirements of the roof of the tank, it may or may not be necessary to include the partitions 32, and where necessary, the number and distribution of the partitions may be varied. For example, where the roof 34 is required to have a high load bearing capacity, the first tank 30 may include a large number of vertical supporting structures such as the partitions 32. it should be noted that the vertical supporting 20 structures may include vertical poles or posts of varying cross sections which may or may not be of a consistent cross section along their respective lengths. For example the vertical supporting structures may be wider at their bases and may taper towards the roof 34. Moreover, the thickness of the walls and roof of the tanks 30, 40 may be varied to improve load bearing capacity and to resist stress forces such as may occur as a result 25 of movement, land slippage or even earthquakes. In the installation shown in Figure 1, the first and second tanks 30, 40 form part of the form work used to define the space occupied by the raft slab 50. The raft slab 50 includes primary building support structures 51 for load bearing walls and typically
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includes rejnforcing in the form of mesh 52, e.g located in the trenches in accordance A ad of the installatiOn process, the site of the withl standard b-uildng practice. As par ecvtosmde to dwelling 10 may be levelled by excavation equipment and Minor excavations ma o stellinerconnecting Pipes 31, 41 and 61. The mesh 52 is typically installed on bar insd dth-e other form work defining the 5 chairs, the tanks 30, 40 are positioned as required and raft slab is installed ready for the concrete pour. ,;Ia ~ ~ ~ ~ l inse 45sate ed and two Outlets, a supply outlet 4 The second tank 40 includes a single inlet 45 and an overflow outlet 47 which permits overflow from the second tank 40 to be delivered to a storm water drain, another holding tank or the garden, as appropriate, via ic overflow pipe 62. Against gravity, the water storage system provides a water pump 60 operable to draw water from the second tank 40 via the supply outlet 46 through the interconnecting pipe 61 and up to a water outlet appliance 63. The pump 6 is located just above ground level 64 for ease of access for maintenance and repair. 15 Returning to the preliminary tank 20, it can be understood that in periods of low rainfall or higher water usage, the water level regulation means in the form of the ballcock 22 is effective to operate a valve 23 whereby to maintain a water level in the preliminary tank 20, first tank 30 and second tank 40. In Figure 2, there is shown a second water storage system 2 but which is not an 20 embodiment of the present invention. In Figure 2, the components are substantially the sane as the water storage system I shown in Figure 1 with the exception that the interconnecting pipes 71, 72 and 73 are not located at a sub-level relative to the first and second tanks 30a, 40a, but rather are located in horizontal orientation at the level of the base 33a, 43a. Moreover, the first tank 30a and second tank 40a are each hollow 25 structures similar to the second tank 40 shown in Figure 1, i.e. without compartm.entalisation. i will also be seen from Figure 2 that the respective roofs 34a, 44a are not load bearing and that, indeed, there is a gap between the bearer 83 and the respective roofs 34a, 44a. 12 It can be seen that the first nd second tanks 30a, 40a are located in the interstices ete the double brick walls supported by the footings 81 and the stump line- 2 nte btive first and second tanks 30a, 40a. interposed between the respeb a persO skilled in the art that, in some circumstances, it will be understood byaPrlyor 'ointly installed in a p'r- 5 the first and second tanks 30a, 40a may be separat circumstances, it existing building structure where there is sub-floor access. In suchrcednbtween t may be necessary to custom design the rank 30a to enable it to be inserted between the footings or the stump lines as required. Fure 2 operates in similar manner to In operation, the water storage system 2 of Fig 10 that of the first water Storage system I described with reference to Figure 1. Throughout the specification and claims the word "comprise' and its derivatives are intended to have an inclusive rather than exclusive meaning unless the context requires otherwise.moicaonar It will be appreciated by those skilled in the art that many modifications are i5 variations may be made to the embodiments described herein without departing from the spirit or scope of the invention. 13