Benefits of healthy rainwater tanks, maintenance and safeguards

Installing a rainwater tank saves both water and money.  A rainwater tank provides the following benefits:

  • Free water; saving money on water rates.
  • Soft water that lathers easily, saving on soap and detergent.
  • Extra water available for washing cars, watering gardens etc.

The current view of many health authorities is that while rainwater from a well-maintained system is a useful source of water, it is never recommended for drinking water use, and additional treatment may be desirable, particularly in urban areas, for other uses that involve human contact.

High quality tank water is dependant on the owner’s maintenance of a healthy tank.  Proper maintenance involves the cleaning of gutters and downpipes and checking for mosquito and vermin control. Tank installation could include a “first flush” system to divert the initial scour of dirty rainwater away from the tank.

If water is only to be used for non-drinking purposes, such as in the washing machine or toilet, then it is unlikely that any treatment will be required, although filtering does limit some contamination. If water is to be provided for other household uses that involve contact with humans, such as drinking, showering or cooking, additional treatment should be considered; potentially ultra-violet disinfection.

While we support rainwater harvesting we do not suggest that tank water replace an available town water supply for drinking purposes. This is because there is no guarantee that every resident installs, cleans and maintains rainwater tanks correctly to ensure safe drinking water.

Maintenance Checklist and schedule

Regular inspection of your tank is recommended. A thorough maintenance schedule is provided in the brochure – Rainwater Tanks  and a simple checklist can be obtained by contacting us.

Monthly inspection: This should involve checking the tank strainer and tank overflow screen for any breakage where mosquitoes can enter. Clean them monthly throughout summer wet season and three monthly from Autumn to Spring.

Three monthly inspection: Check and clean first flush devices, and leaf guards on rainheads. Check the roof and clean gutters of plant material and other potential contaminates. If large amounts are found, then inspection and cleaning should be done more frequently, especially after heavy rainstorms. Prune overhanging tree branches and foliage. 

Six monthly inspection: Check tank for defects and repair.Visually check water quality; ensure water is clear and contains no unusual smells.Check for evidence of animal, bird, or insect access including mosquito larvae; if present locate and close access points. Check for algal growth; if present, find and close all sources of sunlight infiltration.Ensure all rainwater outlets have the correct signage.

Yearly: Check tank structure and base for structural integrity. Remove accumulated sediment sludge from inside the base of the tank.

Public Health Issues

Approximately 3 million Australians currently use rainwater for drinking with very few reported incidences of ill health. This is in spite of a number of reports that have shown that tank water often fails to meet microbiological guidelines for drinking water quality because of contamination by animal faeces, vegetation and air-borne pollution.

The current view of many health authorities is that while rainwater from a well-maintained system is a useful source of water, additional treatment may be desirable, particularly in urban areas. If plumbed in to the potable (town drinking water) system, back-flow prevention is an essential barrier to protect the potable system from possible contamination. Tanks must be installed in accordance with plumbing standards.

To help ensure the integrity of your  rainwater tank, the quality of the collected rainwater, and the safety of the community against disease, follow the simple maintenance checklist.

Tank water safeguards

When installing a rainwater tank attaching several simple devices may assist in keeping the tank water quality in reasonable condition.

Gutter guards prevent leaf litter entering the tank
If leaf litter enters the gutter, this debris may accumulate and block the rainhead or inlet screen causing uncontrolled overflow and reduce the amount of rainwater collected.

Rainhead diverts leaves
Installing a screened downpipe rainhead on each down pipe just below the gutter sheds leaves, preventing them from entering the tank. Self cleaning types are recommended.

First flush diverter redirects the first polluted flow
Pollutants and debris washing off the roof in the first runoff (20 litres/100 sq.m.) are redirected to the overflow drainage system, protecting the tank from excessive collection of sludge and subsequent organic and chemical contamination. First flush devices need to be cleaned regularly to function well.

Mosquito and insect screens are required to be fitted on all rainwater tanks
The screen gauze must have a diameter no larger than 1mm aperture mesh

Filters provide additional protection
Various types of filters are available that protect against micro-organisms, chemicals, fine sediments, colour and odour. to perform well they need to be replaced regularly.

Backflow prevention device prevents untreated water contaminating the town water supply
If there is an interconnection between the rainwater supply and the town water service supplying the outlet valve at fixtures and appliances, such as toilets and washing machines, an appropriate backflow prevention device must be installed to protect against the untreated water in the tank accidentally contaminating the town water supply.

Roofing materials may influence water quality
Rainwater should not be collected from a roof with lead flashings or older painted surfaces which may contain lead.

Positioning of the tank outlet
The outlet should always be above the base of the tank to avoid drawing off sediment that has settled at the bottom of the tank over time. the tap or outlet should be marked "rainwater" in accordance with Australian standards.

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