In your home

Why install a rainwater tank and grey water system

Yarra Valley Water recognises that our customers want to take action in their homes and gardens that will reduce their impact on the environment.

Water is increasingly precious due to unreliable rainfall and increased demand; but households have the power to make a difference by adopting sustainable solutions around the home.

To search and compare a range of solutions for rainwater collection and storage, visit the savewater product directory.

Benefits

Water captured in a rainwater tank provides an alternative water supply exempt from water restrictions which can be used to:

Flush toilets
Fill washing machines
Supplement garden watering
Wash the car, and
Top up ponds and pools.

Other benefits of installing a rainwater tank are:

Protecting your valuable garden
Add value to your home
Use the water you collect when and how you want, free of water restrictions
Save on water usage and therefore money

Rainwater tanks - How do they work?

Rainwater tanks store rainwater run-off from your roof. In most cases, the water from your roof is funnelled along your gutters and into downpipes connected to your tank. If you are going to install a rainwater tank, alterations to your guttering may be required. To get the best out of your rainwater tank, it’s important to install appropriate screens to stop debris and insects entering the tank.

How much water do you need?

The average Melbourne household uses 157,000 litres of water a year. Below is an approximate guide to how much rainwater your home could collect over one year if your tank(s) are installed in the right location(s). Generally 1 mm of rain on 1 sqm of roof space will deliver 1 litre of water into your tank. To help you calculate your potential savings, note that: An average single carport is approximately 25m square metres The roof of an average 3 bedroom house is approximately 150 square metres The roof of an average 4 bedroom house is approximately 200 square metres The roof of an average 5 bedroom house is approximately 300 square metres.

Average

Annual Rainfall (mm)

Roof Area (sq.m) and litres (L) collected over 12 months*

25sqm

150sqm

200sqm

300sqm

653

12,244L

73,462L

97,950L

146,925L

* Figures based on 75% roof efficiency - improved design & installation can significantly improve the water collection efficiency

To maximise the water collected in your rainwater tank consider the:

Roof catchment area and down pipe location (configuration is key to maximising water collection)
How much water your household needs
Rainwater tank capacity

By connecting your rainwater tank to your toilet and laundry you can extend your tank’s use in winter when you do not need to use the water for outside. Using rainwater for internal use as well will save two to three times more water than a tank used for garden watering only.

Choosing the right tank

When selecting the size of the tank there are a number of things to consider:

What is the water demand of your home?
How many people are living in your home?
What is your intended use of the rainwater?
What reliability do you want from your tank?
What is the total area of roof draining into your tank?
What is your area’s average rainfall?
Do you need extras like a pressure pump, the ability to top up your tank with drinking water, a backflow prevention device or a first flush device?
Are the materials used on your roof suitable to collect rainwater?
Are there physical constraints for your property that may influence the type of rainwater tank you need?

Savewater has some good tips for how to select a rainwater tank.

To allow continuous rainfall collection, you need to be consistently using your tank water all year round. We recommend plumbing your tank to your toilet or laundry; if tank water is used for your garden alone, your tank will remain full and unused during the winter months when your garden does not require watering.

It’s important to find the right location for your tank and consider the space you have available. Tanks can be installed above and below ground and multiple tanks may be installed either connected or installed separately. It is recommended that you install the largest tank that you can afford and fit on your property. For the average home 3,000L to 5,000L would normally be sufficient. Larger requirements such as an extensive garden may need a much larger tank of 10,000L or greater.

Installation - getting it right

When considering the location of your tank try to find a space close to the house and near existing downpipes and guttering. Remember the more downpipes flowing into your tank the more water will be collected. Designing the drainage infrastructure is a critical component of installing a tank where maximum rainfall falling on your roof is collected into the tank. If you are plumbing your tank to the toilet and or washing machine it is best to locate the tank as close to these fixtures as possible to minimise complex pipe work. The tank needs to be installed on level ground.

Pumps and other equipment

Most properties will require a pump to deliver water from the tank around the property. Gravity systems drain the water from the tank by placing the tank on a stand and directing flow in the direction needed, however a pump is the best option for targeted results. There are a variety of pumps on the market so it is best to ask the plumber installing the tank for expert advice regarding your specific pump requirements. To reduce the amount of sediment and debris entering a tank, mesh screens and ‘first flush diverters’ can be fitted. A screen will filter large debris such as leaves and sticks while ‘first flush diverters’ store the ‘first flush’ of the rainfall that carries the sediment and other pollutants washed from your roof.

Maintaining your rainwater tank

Rainwater tanks are generally low maintenance; but regular cleaning and maintenance is advised. Over time sediment will build up on the bottom of the tank, this requires cleaning every 2 – 3 years. To minimise sediment:

Ensure gutters, tank inlets and screens are clean and free of debris
Ensure the roof catchment has no moss or lichen
Prune overhanging branches to reduce leaf litter

To minimise the risk of algae and larvae contamination in your tank, ensure there are no entry points for insects or small animals. If contamination occurs it may need to be treated – ask your council for advice.