If you are installing a cold water storage tank to hold drinking water, you may have your own private water supply, particularly if you live in a rural area. The water storage tank could be a rainwater tank connected to your roof, or a tank connected to a nearby stream, bore or reticulated water supply.
Likely health risks
Your drinking water supply can become contaminated with harmful microorganisms (or pathogens) including viruses, bacteria and parasites.
Generally, these come from human or animal faeces, such as contamination from a leaking septic tank
and on-site waste water management system if you have an underground tank. On-site waste water management systems can also contaminate other water sources (such as a nearby stream or bore) if they’re not properly maintained. Water in irrigation channels and streams can be contaminated with pathogens from run-off from farming activities, making it generally unsuitable for drinking if not properly treated.
These pathogens are not visible to the naked eye and may be present in water that appears to be clear. Drinking water that contains pathogens causes gastroenteritis. Children, older people and people with suppressed or weakened immune systems are the most vulnerable to these pathogens.
You can reduce the risks by ensuring your drinking water comes from a reliable source and by regularly maintaining your water supply system.
Chemical and heavy metals contaminants can also pose a health risk, although they are usually less common than other contaminants:
- soil from previous industrial, mining or agricultural activities, which may contain contaminants. Dust can be blown on your roof and washed into your rainwater tank, leading to chemical residues and other contaminants that can build up in the water over time
- crop dusting, which can result in agricultural chemicals entering rainwater tanks from roof catchments, irrigation channels, streams and dams
- residues from solid wood fired heaters, which can condense near flues on your roof
- residue from lead-based paints or lead flashing on older roofs and gutters, which can be washed into your rainwater tank
- run-off from roofs in urban or industrial areas, which can contain chemical pollutants from the air.
In some parts of Tasmania, groundwater may contain elevated levels of substances such as arsenic and nitrates. Materials used to manufacture tanks (such as lead solders or non-food grade sealants) can also be harmful to your health.
Generally, water that is cloudy or dirty will not be suitable for drinking unless it is properly treated. It is usually more cost-effective to obtain your water from a good quality source than to treat poor quality water so it is safe to drink.
However, if your drinking water supply does require filtration, make sure the filter complies with the relevant Australian Standards (you can check with your plumber, supplier or manufacturer) and be sure to follow the maintenance instructions.
In most rural areas of Tasmania, rainwater that is collected from a clean roof and securely piped into a well-maintained above ground tank shouldn’t need to be disinfected.
Groundwater from cased deep bores also shouldn’t require disinfection.
Groundwater obtained from a shallow bore should be disinfected in case the bore has been contaminated with farm waste or effluent from septic tanks.
If you suspect your water supply has become contaminated with pathogens, you should disinfect it before using it for drinking, preparing food, making ice or personal hygiene.
Inexpensive and effective options include boiling the water that you drink and adding chlorine to the water supply. These are detailed below.
Another option is using ultraviolet light. However, ultraviolet light systems require very clear water to work effectively, and must be carefully designed, maintained and operated.
- Bring the water to a rolling boil; use an electric kettle with an automatic shut-off.
- Allow the water to cool before storing it in a clean container until it is needed.
- For further guidance read the Tasmanian Plumbing Code 2013.
Use enough chlorine to provide a free chlorine residual of around 0.5 milligrams per litre (mg/l) after 30 minutes. As a general guide, an initial dose of 5 mg/l will provide this residual. You can test the residual in your water tank with a swimming pool test kit or dip strips (available from pool shops and suppliers).
Follow the safety and handling instructions on chlorine containers. Wear proper hand protection and always wear eye protection when handling or preparing chlorine solutions.
After chlorinating, you should ideally wait at least 24 hours before using the water (to allow the pathogens to be destroyed). The chlorine may leave the water with a taste and odour, but this is harmless and should disappear in around 10 to 14 days. Boiling the water will also remove most of this taste and odour.
For further guidance read the Tasmanian Plumbing Code 2013 on use of rainwater tanks (see the end of this guide for details).
A dead animal in your tank will not necessarily cause illness if you drink the water, but it is best to drain all water from the tank as a precaution.
Wash out any sludge from your tank, block or repair any holes in the tank roof, and scrub the interior with a household bleach solution.
Maintain good ventilation whenever you are cleaning out any tank and always work with an assistant outside the tank.
Refill your tank with good quality water and disinfect it with chlorine (as detailed above). Alternatively, you can refill the tank with water purchased from a commercial water carrier – this water is already chlorinated.
If good quality water is in short supply and it’s not feasible to drain and refill the tank, remove as much of the animal carcass as possible and disinfect the water with chlorine (as detailed above).
Generally, your drinking water supply shouldn’t need to be tested if it is well managed and maintained.
However, if you do need your water tested, most analytical laboratories can provide this service. Look in a business telephone directory under ‘analysts’ or Contact Council.