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Water Tank Contamination

Posted by Rod Judge on

In Australia, the rate of rainwater usage as drinking water is much higher than in other countries. Authorities consider the risk of using rainwater as very low and health authorities have noted no correlation with the use of rainwater for drinking and waterborne illness in Australia.

To maximise the quality of your rainwater, WaterNeeds recommends regular water tank maintenance to ensure water quality remains stable, particularly if your water tank is used for potable drinking water.

If you become concerned your water tank has become contaminated, we’ve listed below some common contaminants and how to avoid them affecting your water.

In NSW, water is considered safe to drink if there is no visible discoloration, no noticeable smell and no noticeable taste¹.


Rainwater is free from contaminants, however contamination can occur when particles are collected in the air as the rain falls, or when airborne contaminants settle on rooftops or water collection areas, and are then washed into the water supply when it rains.


If you’re using your rainwater for drinking and cooking, it’s generally considered potable if there’s no colour, taste, or smell, however there are some pathogens and pollutants that are colourless, odourless and tasteless. Filtration such as reverse osmosis, UV sterilisation and ultrafiltration can be used if you’re concerned.


Regular maintenance including roof and guttering checks for plants and debris, maintaining and filter screens around the tank, and occasionally desludging.

Professional services are available for specialist maintenance work such as desludging.


Any material used in the rainwater harvesting system must be free from

  • lead based paints
  • Tar based sealants
  • Chemically treated timbers
  • Lead flashing
  • Fireplace flu
  • Fibrous cement
  • Acrylic paint
  • Air conditioner overflow
  • Hot water overflow


Rainwater tanks need to be completely sealed to avoid acting as breeding grounds for mosquitoes.

Another option for avoiding mosquito larvae is to choose an underground water tank where temperatures are too low to sustain the mosquito larvae. Underground tanks are also darker and provide a more unfavorable environment for bacteria and algae to grow and flourish.