How to get the most out of your rain water tank

Check out the health, building and council regulations in your local area, particularly if the rainwater tank is being installed to meet regulatory requirements or if your house is in a heritage overlay area. Your local council can advise what planning requirements apply to your property.

A licensed plumber will be required for some of the work, such as installation of the pipes in and out of the tank (connecting the gutters to get rainwater in and an overflow pipe for excess water to go to the legal point of discharge to council stormwater drain). They are also required for connecting the tank to toilets and/or your washing machine.

The tank will be heavy when it fills with water so it must be installed on a strong, level and stable foundation.

Place the tank in a location where you can easily access it for maintenance, and you can collect as much rainwater as possible from your roof. Often this will mean collecting from more than one downpipe. Your licensed plumber will be able to advise you on this.

Maximising the roof area flowing to your tank and connecting as many appropriate indoor uses as possible will save the most water. Ask your plumber about connecting multiple downpipes and using rainwater in all toilets and the laundry.

A rule of thumb for an optimal tank system is to connect 60% of your total roof area to a tank that has 2,000 litre capacity for every 100 square metres of roof area harvested. Your plumber or the design team for the new building will be able to do these calculations and advise you on the size and type of tank you require.

A typical house in Melbourne will need between 2,000 litres for a small townhouse and 5,000 litres for a medium size 3-4 bedroom house.

If your tank is connected to internal uses your plumber should install a mains back-up system. That way if your tank runs dry you can still flush your toilets and use the washing machine.

Downpipes can deliver rainwater directly to the tank by gravity if there is enough of a slope from the downpipe to the rainwater tank and when the tank is close to the house.

If there isn’t enough of a slope from the downpipe or the rainwater tank is further from the house for example next to a fence, a charged stormwater system might need to be installed instead. These systems have pipes that run underground and then come back up at the tank. It works because the water pressure on one side pushes the water up and into the tank on the other side. Charged stormwater systems are often useful if you want to connect additional downpipes to your rainwater tank to collect more water from your roof.

Note that a qualified plumber is required for any work on your gutters/downpipes and charged stormwater systems.

There are a variety of rainwater tank shapes, materials and colours to match your property and available space.

Your budget and the planned location of the tank will influence the type of tank you need.

A small external pump is generally used for simple residential use. This will depend on your property size and how you use rainwater in your home. Multistorey houses and properties with significant slopes may require larger pumps.

Consider adding energy-efficient accessories like a pressure tank to your pump. These reduce the number of times your pump runs, saving energy and maximising the pump's life.

You will need a licensed plumber to install your rainwater tank, as connections to downpipes and internal uses is regulated plumbing work. We recommend you hire one who is experienced with rainwater tank installations. Consider getting more than one quote and make sure you do your research first.

You can check if someone is a qualified licensed plumber by checking the Find a Plumber tool on the Victorian Building Authority (VBA) website. The VBA are the Victorian building and plumbing regulator.

After installation your plumber should provide you with a certificate of compliance for the plumbing work. You may also need an electrician to provide a safe power supply for your pump and a tradesperson to lay the foundation for your tank.

During installation

• Check that your roof and guttering are suitable for collecting rainwater. Don't collect rainwater from roofs with lead-based paint or flashing, bitumen-based products, or exposed treated wood.
• Prevent blockages from overhead trees and vegetation by trimming them or installing gutter guards.
• Check that your rainwater tank inlet and overflow are mosquito-proof and ensure there are no other entry points for insects, vermin and debris.
• Use a first-flush device. This is a simple and effective way of only letting the cleanest water into your tank.
• Install a mains switching device to supply drinking water when the tank is empty. Your plumber will be able to advise on the plumbing requirements, connection requirements and back flow requirements to protect the mains water supply.

There are a few things you can do to confirm that your system is working:

1. Check for rainwater in the tank

Consider installing a tank level gauge or knock on the side and listen for water. If you practise knocking at different heights on your tank you will quickly learn the sound that indicates the water level. If there hasn’t been much rain recently, the water level might be low. If it has rained recently and your tank is empty, there may be a blockage at the inlet or a leak. If the tank is full after an extended dry period, then check your pump is working.

Never enter your rainwater tank. Tanks are confined spaces which can be hazardous. Engage a plumber or tank cleaning professional if your tank needs unblocking or cleaning.

2. Check if your pump and mains switching device is plugged in and turned on

If your rainwater system uses a pump, you'll find it inside or outside your tank. Check that the pump is plugged in and turned on, and the outlet tap from the tank to the pump and mains switching device are open.

After a power surge your pump might need manually resetting. If your pump is not running after a power surge, follow the manufacturer’s instructions to turn it back on. There is normally a simple safety button or switch on the pump.

3. Check if you're using rainwater

Turn on your garden tap, flush a toilet or turn on your washing machine – whatever is connected to your tank. You should hear your pump starting up.

After a power surge your pump might need manually resetting. If your pump is not running after a power surge, follow the manufacturer’s instructions to turn it back on. There is normally a simple safety button or switch on the pump.

If your pump still isn’t switching on or you’re unsure if your tank is connected to your toilets or washing machine, contact a plumber to arrange an inspection.

Here are some simple ways for you to keep your rainwater system working in top condition:

1. Check and clean your gutters, screens and downpipes

Gutters and downpipes carry water from the roof into the rainwater tank. If they fill with leaves or debris, it can affect water quality or even block flow completely.

You can prevent blockages and improve water quality by:

• cutting back overhanging branches or vegetation
• cleaning your gutters, screens and downpipes
• removing leaves and debris from your roof
• installing a gutter guard and downpipe screen.

2. Check your first flush device and flow restrictor

When it starts to rain, the rain will wash dirt and leaf litter from your roof and gutters into your rainwater system.

Some systems have a first flush device that diverts the first flow of dirty rainwater to a separate chamber, stopping it from entering your tank. This chamber slowly empties the dirty water through a flow restrictor. The flow restrictor can block easily, so it's important to clean it out regularly. You could clean your first flush device at least after every heavy rainfall event.

3. Check your tank inlet screen

The tank inlet screen stops leaves, debris and mosquitos getting into your tank.

Clean the screen regularly by removing any leaves and debris. Some screens can be removed and rinsed with a hose.

If your screen has holes in it, replace it as soon as possible.

4. Fixing problems and further help

Many problems can be fixed or prevent by following the simple steps listed above. If you need further help, contact a licensed plumber or your rainwater tank supplier.

If you have a dispute with the rainwater tank supplier, installer and/or plumber, there are dispute mechanisms available. Depending on the nature of the dispute, the following are possible contacts.

• For contractual issues contact Consumer Affairs Victoria – they provide free and impartial advice to property owners and tradespeople on their rights and responsibilities when building or renovating.
• Domestic Building Dispute Resolution Victoria is a free government service designed to help building owners and builders resolve residential building disputes.
• For work involving plumbers, contact the VBA for any disputes relating to non-compliant work.