Water tanks

Round water tank
Round water tank, 12,500 litres

Connecting a ”’water tanks”’ to the down spouts of your home’s guttering system is one of the easiest ways to contribute to sustainable living.

Regulations as at May 2007

  • In Canberra in the ACT, new developments must include a water tank.
  • In Sydney and NSW, new building regulations call for a 40% reduction in mains water usage.
  • In Victoria, new homes will have to be 5-star standard, and must install either a solar hot water service , ”’or”’ a water tank (minimum size 2000 litres).

Rules and rebate schemes are different in each state.

With the current low rebate schemes and the low cost of water the reasons for installing a water tank tend to be altruistic rather than financially motivated: for the cost of installing a 9000 litre tank, you can buy more than 5 million litres of water from Sydney Water.

Assessing your situation

So if it is not for financial reasons why are you installing a water tank?

Here are some reasons:

  • Do your part for water conservation
  • You can water your garden with some independence from water restrictions
  • Make rain water available for drinking in your home
  • Use rainwater in the laundry and toilet

What size water tank should I choose?

Get the biggest tank you can fit in your garden. As a rule of thumb, about 25,000 litres (5,000 gallons) of storage is considered enough for a small family to be nearly self sufficient for normal domestic usage. The storage size will vary according to local rainfall. Dry areas would require more storage, wet areas less.

Water tank under deck
Water tank under deck

Rainwater diverter – a cheap and simple solution

You can get started with some rainwater collection by installing diverters in downpipes and filling a large garbage bin, but with this system there is no “first flush diverter” to remove impurities from the first quantity of rainwater from the roof. Water can be distributed from the bin/tank using gravity or a small pump.

Rainwater diverter

Types of Water Tanks

  • ‘Cyclindrical tanks’ – either plastic or galvanised iron – are often the cheapest, but they require a lot of space
  • Rectangular and other narrow tanks – either plastic or galvanised iron – can fit under eaves and in narrow spaces next to fences. However, they are lower volume and more expensive.
  • Collapsible bladder systems can be installed under houses between existing stumps. However, these are the most expensive.

Other Considerations

  • If you use tank water for showering, be aware of the difficulties matching different water pressures. The mains pressure is often higher than what a pump can produce and the mains pressure can stop the tank water from coming through the pipes.
  • There are strict government regulations concerning the connection of mains water and tank water systems. The intention is to prevent tank water systems possibly contaminating the mains system. A licenced plumber must install this type of connection. These regulations don’t apply if the systems are plumbed seperately.
  • The ability to fill tanks also depends on the roof catchment area you have. If the catchment area is too small you may never fill large tanks. This can be calculated from the average rainfall events for your location and the roof area.
  • In city areas use a green plumber. Many urban plumbers are not acquainted with installing and connecting rainwater tanks, systems and pumps.


  • Larger tanks will often need to be installed in back yards using a large crane to lift it over the house roof or back fence (if there is rear access).
  • Check with the tank retailer for the cost of using a crane. Some retailers will offer a free crane install for tanks over a specific size, below that size you may have to pay separately for the cost of the crane hire (which could be $300 to $500).
  • Tanks can be partially buried – up to a third the height of the tank is usually possible. If you bury tanks deeper than that without taking special measures they can “pop out” of the ground if the tank is empty and the water table rises. A drain system around a buried tank site with a sump and water pump installed could avoid this happening and enable the tank to more fully or completely buried. This type of installation should be done professionally.
  • Ensure that every tank has a valve installed at its outlet. This will allow you to isolate the tank quickly and easily to work on the pipe system. Also, if you damage the pipe outlet system you can shut the valve to prevent the entire contents of the tank being lost.
  • Tanks can be installed under decking if the decking support structure is designed to leave space underneath to accommodate the tank.
  • All tanks must have an overflow connection to stormwater (or perhaps another lower tank).
  • Choose your [water tank pump] carefully – it is very important to calculate the pressure and flow required to get the appropriate performance.

See also

  • [Water tank pump]
  • [Swimming pool] – convert your swimming pool for water storage
  • [Melbourne water usage]

Commercial links

External links