Whitehorse City Council

Water Tanks

EnvironmentSustainabilityWaterTankWater tanks can help reduce and slow the flow of stormwater into local creeks and rivers and reduce the need to use mains water.

By installing a water tank, residents have access to an additional source of water and can make an important contribution towards reducing the demand that we make on dam storages. Commercial, industrial and retail properties can also take advantage of this supplementary water supply.


Advantages of Water Tanks

  • Rainwater is generally much lower in salinity than mains water. This reduces the corrosion of in-house appliances and may extend their life (including hot water services, kettles and irons) and is also good for low salinity plants in the garden
  • Once the tank is installed, rainwater is cheaper than bottled water or mains water
  • Being softer than mains water, rainwater may help reduce the amount of soap, shampoo and detergents you need to use
  • Using a water tank regularly may reduce stormwater runoff from your roof. This may reduce flooding, erosion and environmental damage to our streams and coastal waters. Tanks can also reduce the peak load on the reticulated water supply system
  • Water tanks provide a secondary backup water supply for your home should there be a failure or reduction in the main supply
  • The economic benefits to the community from the use of rainwater tanks are derived from mains water savings, construction and depreciation savings resulting from a reduced requirement for storm water infrastructure and interest earned on community savings due to the deferral of new water supply dams
  • Water tanks utilised for outside uses together with toilet, hot water and laundry uses can give significantly more benefit in reducing potable water supplied to homes than individual demand management strategies such as AAA showers or tap fixtures.
  • Rainwater is not treated with chemicals, including chlorine


Water collected in water tanks is suitable for a variety of domestic and industrial uses, such as garden irrigation, toilet flushing and processing. Council does not recommend that it be used or consumed as drinking water without additional filtration.

Prices of water tanks vary according to size, make, installation, additional fittings and suppliers. With the cost of water likely to increase, installing a water tank or water bladder to capture rainwater is a good environmental and financial investment.

More Information About Water Tanks

Water Tank Bases

Most metal or plastic tanks must have a stand or base to carry the combined weight of the tank and water. Most flat-bottomed tanks are not able to carry the heavy load of water without the support of a strong, level and continuous base.

When a water tank is full, every kilolitre of water weighs 1000 kilograms (one tonne) so for safety it is important to construct a tank stand that is strong and stable. When a rainwater tank is empty it can be blown over by strong winds, so make sure your tank is adequately secured to the stand. Lightweight stands should be securely fixed to a heavy footing.

If you are intending to use a pump to distribute the water, the water tank can be at almost any level. If you wish to feed the water by gravity it is usually necessary to elevate the rainwater tank on a sturdy stand.

To prevent external corrosion, the underside of metal rainwater tanks should be kept above the ground and sit on a self-draining base.

Underground water tanks must be sealed against the entry of surface run-off, groundwater and leaking sanitary drains that may contain pesticides, fertiliser and animal (or human) faecal material.

Care should be taken not to place rainwater tanks inside the drip-line of a tree canopy. Root growth can damage the base of tanks. Trees may fail to thrive if rain cannot get to the roots.

Covers and Lids


A rainwater tank should have an impervious cover to prevent the entry of dust, leaves, pollens, debris, vermin, mosquitoes, birds, animals and insects. It is essential to seal access hatches with strong, close-fitting, childproof lids. 

Screens and Strainers

The inlet to the water tank should incorporate a mesh screen or strainer to prevent the entry of live insects and to catch leaves and undesirable roof deposits. A mesh with openings smaller than one millimetre is very effective against mosquitoes. The tank overflow should also be protected with an insect-proof mesh.

First Flush Rainwater Diverter

For added protection a 'first flush' water diverter can be installed to divert the first flush of rain (containing roof dust, leaves, droppings, etc.) to the stormwater and then direct clean water into the rainwater tank. First flush diversion valves can be fabricated using plumbing fittings or purchased as a complete commercial unit.


Light Proofing

Tanks, covers, plumbing pipes and fittings should be light proof to minimise daylight penetration and algal growth in the water.



If the water tank cannot be elevated sufficiently to give adequate pressure to appliances, it may be necessary to install a pressure-boosting pump. The float valves in toilet cisterns, irrigation sprinklers and the solenoid valves in washing machines (or dishwashers) may not operate effectively without adequate pressure. The size of pump will vary according to the height of the tank, height of the appliance, diameter of plumbing pipes and the flow requirements of appliances. The services of a hydraulic specialist and/or pump supplier may be required.