In some cases it may be necessary to augment rainwater in tanks with water from other sources such as bores, dams, rivers and creeks or with carted water.
Only water that is suitable for the intended purpose should be used. If the water is to be used for drinking and food preparation, it should comply with the guideline values cited in the ADWG (possibly after chlorination). If there are any doubts about the suitability of a water source, consult the relevant local or state/territory water or environmental health agency and, if necessary, have the water tested before adding it to the tank.
Surface waterWater subject to potential contamination from human or livestock waste, such as dams, rivers and creeks, can contain a wide range of pathogenic organisms including chlorine-resistant Cryptosporidium. Water of this type may not be suitable for drinking even after disinfection.
Surface water that is protected from human and livestock waste can be used. Water should be added to the tank in one action, then chlorinated and allowed to stand for at least one hour before use.
Chlorination should be performed as described in Section 5 using a test kit to measure chlorine residuals. If, 30 minutes after chlorination, the free chlorine is not at least 0.5 mg/L, a second equal dose should be added. If a kit is not available, use double the amount of chlorine recommended in Section 5.
Deep groundwater, confined aquifersWater from a deep, encased and well maintained bore and/or from a confined aquifer will generally not need disinfection after addition to a rainwater tank, but the chemical quality of some groundwater is not suitable for drinking. Only groundwater that is compliant with guideline values cited in the ADWG should be used. Key health parameters for groundwater are arsenic, nitrate, fluoride and health-related heavy metals. Salinity is an important aesthetic parameter.
State or regional water resource agencies may be able to provide general information on local groundwater characteristics.
Shallow groundwaterGroundwater from shallow or unconfined aquifers is readily contaminated by agricultural, industrial or urban activities and generally should not be used as a source of drinking water unless it has been recently tested for microbial and chemical quality (for example, for arsenic, nitrate, fluoride, health-related heavy metals, petroleum hydrocarbons and other organic chemicals).
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Carted waterDrinking water is recognised in Australia as a food and, depending on state/territory legislation, water carters/carriers may need to be registered as a food business. If the supply of additional drinking water is needed, local authorities should be able to provide names of suitable water carters that are registered or that the authorities are satisfied will provide water suitable to drink. In the absence of information from local authorities, make sure the water carter can provide evidence that water supplied will be safe to drink. This evidence could include:
- any authorisations issued for the purpose of supplying drinking water
- compliance with state/territory food legislation including, where required, that they have notified the local council or appropriate health authority that they are a food business
- the identity and quality of the source water
- proof that tankers used are suitable for the purpose of carrying drinking water (for example, not likely to have carried other materials that would contaminate drinking water)
- a record of a chlorine residual.