Traditionally water from rain water tanks has been considered one of the purest sources of drinking water available.
However there are a number of contributing factors which might mean that this is not always the case.
The best solution for filtration of water from rain water tanks depends on a number of factors.
Some important considerations are:
The type and age of the rainwater tank
Clearly a new, fully sealed rain water tank is less likely to contain contaminants than an older style open topped tank. Older tanks may contain dangerous levels of heavy metals such as copper and lead from corrosion of the tank internal surface or the pipe-work used to transfer the water for use.
Location of the rainwater tank
If the rainwater tank is located near to sources of airborne impurities such as busy roads, industrial plants, loading docks, fertilizers or other potentially hazardous contaminants H2Only highly recommends having the water tested by a reputable laboratory before deciding on the best method of filtration.
Run-off source
Rain water can be collected from a number of run-off sources, the most common being an adjacent roof area. Leaves and other organic matter on such areas can contribute to particulate matter collecting in the water causing discolouring and turbidity. Animal faeces and other matter can risk contamination of the water by various micro-organisms such as bacteria, in particular coliform bacteria such as E. coli. Many roof areas contain lead flashing and other metallic components which may leave traces of heavy metal contaminants in the water. If you are doubt about the surface run-off area H2Only recommends that the water is tested to identify possible contaminants before a water filtration solution is recommended.
Other considerations such as the intended use of the water must be considered. Drinking water filtration obviously requires a much more carefully considered filtration solution than for watering gardens or use in washing appliances.
The water pressure at the filtration site must also be considered. Generally speaking better quality water filtration requires higher pressure to work effectively.
For the best advice on the water filtration solution in your unique circumstances please contact H2Only for more information. If you would like to get a sample of the rain water analysed H2Only recommends the following NATA registered laboratories.
Go to Agri Nutritional Services
MPL
Stage 1. Sediment Filtration
This stage consists of a fine sieve filter to remove the larger suspended particles from the water. If there is sufficient pressure (usually where a pump is installed) we recommend a polyspun 10-micron sediment filter. Where pressure is low (say below 100 kPa) we recommend a low pressure pleated filter of between 5 and 10 microns in size.
Stage 2. Disinfectant
To ensure that bacteria and other micro-organisms do not infect the water we recommend a disinfectant be added to the water in the tank. Having evaluated a number of alternatives we recommend Aquasafe, a revolutionary second generation disinfectant designed specifically for the sanitation of rain water tanks.
Aquasafe is a low cost and non toxic disinfectant that is approved by the Health Department of WA for use in drinking water and which is environmentally friendly. Aquasafe contains a stabilised form of H2O2 which oxidises bacteria and pathogens more effectively than most chlorine-based sanitisers and does not leave any toxic residue in the water. Aquasafe comes in liquid form and is simply poured into the rain water tank: each dose protects your water for up to 2 months.
Other Suggested Protections
Unless you are located close to major industry or roads is unlikely that the levels of chemicals in the water would be significant and therefore it is generally not necessary to install an activated carbon filter to remove such chemicals. However it is important to ensure that you do not spray chemicals including herbicides, pesticides and fertilisers near to either the tank or the collection surfaces.
Keeping collection surfaces clean and clear of debris will help to reduce the contamination in the water. Sealing the tank at the top and maintaining grates on the collection surfaces will prevent large pieces of debris and dead animals, birds and insects from entering the tank. The rain water tank should be emptied and thoroughly cleaned periodically to remove the silt at the bottom.
If possible it is also extremely beneficial for the quality of your drinking water to locate the outlet pipe from the tank approximately 18cm from the bottom. This will help to prevent the sediment which collects at the bottom of the tank from flowing out into your drinking water.