People in rural areas have long used alternate sources for obtaining water for drinking purposes due to necessity. This has included bore, spring, lake, river and rain water. In recent times there has been an increase in the use of rain water, and where available, bore water by people who have an existing town water supply. This is generally due to the belief that the chemical makeup of these alternate water types is of a superior quality compared to that of the local authority supplied water. This issue of whether this belief is justified will not be addressed here, however, it may be necessary to consult local health authorities and/or have chemical analyses performed before using bore water for drinking purposes. The most common cause for failure of these water supplies meeting established drinking water standards is due to microbial contamination.

Rain Water

The quality of rain water will be dependent upon the degree of wildlife that have excess to the roof area and build up of vegetation. Plant matter provides nutrient source for bacteria and animals leave faeces which may be then washed into the storage tank unless the tank system flushes the first water flow onto the ground.

Bore and Spring Water
Contamination of these water supplies by harmful bacteria or parasites is not common. However, leaching into the water table and surface contamination can occur. Pump heads, ruptured or cracked pipes can lead to colonisation by soil or faecal microorganisms if present in the environment. Pump heads need to be regularly inspected and properly cleaned and disinfected.

Water Storage
With regard to water microbial quality, storage tank maintenance cannot not be overemphasised. Water is not sterile, even properly maintained chlorinated water can have a microbial count of up to 100,000 bacterial in every litre. Non-chlorinated water can have 5 times this level and is still regarded as acceptable for human consumption. This is presuming that other microbial levels such as, coliforms, faecal coliforms and E. coli are within acceptable limits. Have you ever got into a swimming pool that has not been chlorinated and felt the slippery bottom? This can be due to bacteria adhering to the surface, multiplying and producing a slime. The same thing will happen in water storage tanks although it is not always so obvious. This slime can protect the bacteria from any disinfectant added to the water. Soil, sludge and organic matter can also act as a protection mechanism for bacteria. Therefore merely adding chlorine to a storage tank will not effectively disinfect the system. All storage tanks regularly require to be drained and all sludge or other material removed. Then all surfaces need to be cleaned, this can be done by a high pressure hose or by hand. After this, a known volume of water is added and super-chlorinated, then each tap that accesses the tank needs to be opened until the chlorinated water can be smelt coming through the line. The taps are then closed and left for a period to allow disinfection of both the tank and pipe surfaces. The tank is then drained and hosed out to remove all residual chlorine. There are companies (often associated with water storage tank sales companies) that offer this service. The frequency of this cleaning is dependent upon the microbial levels of the water. In general, tanks fed by bore water will require less frequent cleaning as compared to rain water. In general, cleaning at least once a year is necessary, but this can be required up to six times a year in some situations. The only way to ascertain whether the cleaning has been done effectively or that cleaning is required is to perform laboratory analysis for, at least, total bacteria count (plate count) - acceptable level is less than 500 CFU/mL, total coliform count - acceptable level is less than one CFU/100mL and faecal coliform count - acceptable level is less than one CFU/100mL.

Laboratory Tests
The plate count is the level of general bacteria, this may include harmful and/or non-harmful environmental bacteria. Coliforms can come from the soil or may be from animal faecal matter. Faecal coliforms come from animal faeces and indicate that the possibility of other microorganisms that can cause disease may be present. Therefore positive coliform counts and negative faecal coliform counts suggest solely soil contamination. If any of these test results are high, tank disinfection and/or equipment cleaning may be required.