GUIDELINES FOR THE COLLECTION, CARE AND CONTROL OF RAINWATER IN TANKS F A C T S H E E T
Rainwater tanks can provide a supply of good quality potable water with proper management of the tank and roof catchment. The Tank & Reduction of Water Consumption
Tanks are available in galvanised steel, zincalume, fibreglass and concrete and all are suitable for the storage of potable water. Rainwater tanks should protect water from contamination. Contaminants such as industrial pollutants, dust, leaves, pollens, pesticide sprays, fertilisers, debris, vermin, birds, small animals and insects should be prevented from gaining access to the water. Whenever possible tanks should be installed in a shady position but away from trees from which falling leaves might clog screens or contaminate the water. Cover, Lids and Screens Tanks should be covered and all openings provided with close fitting lids or gauze mesh screens. Inlet Screens Water should be screened before entering the tank to reduce the introduction of contaminants which could foul or discolour the water and contribute to the build-up of sludge. Larger contaminant material can be filtered from water entering a tank by a suitably fitted gauze mesh screen. Various in-line screens and filtering devices have been marketed in South Australia. However, if such screens are not available as a standard item they can readily be made to order. Screens and filters need to be positioned and fitted so that they are readily accessible for regular cleaning, particularly where leaves fall onto the catchment area. The locating of the inlet filling pipe so as to discharge in a central position immediately over the tank access opening (manhole), but so as not to inhibit regular cleaning of screening, is a recommended practice. The access opening should be screened in a manner such that the screen mesh gauze fits onto the bottom of a collar approximately 50mm in depth thus providing a sunken dished reservoir on the roof of the tank to allow for effective water entry into the tank. It is not recommended that brass or copper screens be used in contact with galvanised steel tanks nor be in the water which is in contact with the galvanised steel as these materials may accelerate corrosion of the tank. Screening also needs to mosquito proof the tank See details under heading MOSQUITO CONTROL. Algal Growth Light will stimulate the growth of algae in stored water and therefore it is necessary to exclude as much light as possible from the interior of the tank to minimise algal growth. Most algae will not make the water unsuitable for human consumption however, they may affect the odour, colour and taste of the water. As some fibre glass tanks do not completely exclude light, undesirable algal growth may occur. Where this problem exists algal control may be achieved by painting the external surface of the tank. Some new fibre glass tanks are constructed to exclude light and thus prevent algal growth. For this assurance and information regarding painting a tank check with the manufacturer. Where an algal problem exists it is best to drain and clean the tank. The information listed under the heading “Tank Cleaning and Precautions” should be observed. Discard First Rains The first rain after a dry period may wash dust, bird droppings and other contaminants from the roof catchment area and should be prevented from discharging into the tank. An alternative to the above is to hose down the roof catchment area with potable water prior to the first rains and likewise discard the wash down water. First rain or wash down water diversion may be achieved by disconnecting the roof to tank connection pipe. It is suggested that provision for this practice be made during initial tank installation. New Tank Protection Galvanised steel is inherently resistant to corrosion but if the initial corrosion of its surface takes place under suitable conditions a thin adherent film can form which reduces any further corrosion...
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