Maintaining your rainwater tank

If you already have a rainwater tank, you can't take it for granted that you'll always have a reliable supply of rainwater.

Research we've conducted in Sydney has found some common problems tank owners face after a year or two.

We suggest a few simple tasks to make sure your tank provides a clean and reliable source of water while using as little energy as possible.

What do you need to do to maintain your rainwater tank?

If you have a filter on your rainwater tank, you're probably better off without it!

Filters connected to rainwater tanks are usually also connected to a pump.

If you're not drinking your rainwater, a filter is probably providing an unnecessary level of protection. It will almost certainly be costing you much more to run your pump.

Filters for rainwater tend to block relatively quickly. Check them at least monthly until you determine the best frequency for your circumstances.

Some filters can be rinsed clear and re-used several times, while others need to be replaced. Check which type you have and follow the manufacturer's instructions for use with rainwater.

It's unlikely that a water filter will be able to remove any colour in your rainwater supply.

The source of the colour will most likely be in your gutters or at the bottom of your tank. Grit from tiled roofs and leaf litter from trees are common causes.

Diverting this material away before it enters your tank is the most effective way to reduce or eliminate any colour in your rainwater supply.
The gutters and downpipes that divert water from your roof into your tank are a key component of any rainwater tank system. They're also a common oversight for many tank owners.

A blocked gutter is more likely to overflow during heavy rain. An overflowing gutter won't fill your tank nearly as quickly as a free-flowing one.

Preventing leaves and debris from filling your gutters isn't always as easy as it seems. Be wary of expensive solutions before you've at least tested a section with the types of leaves and debris that fall on your roof.

Some effective options may be to get good quality gutter guards or downpipe screens, and/or to clean your gutters regularly.

If you have an above ground tank, you need a screen cover. This will:

  • stop any leaf litter that's passed through your gutter guards or downpipe screens from getting into your tank
  • act as a barrier to any potential vermin that gain access to the top of your tank.


Don't forget to clean your screen cover occasionally!

If your screen is bolted in, you can buy removable tank screens that fit on top of your screens and are easy to remove and clean.

How does a first flush device work?

When it rains, a 'first flush device' prevents the first water from your roof (with the most dirt etc), from entering the tank.

The dirty water goes into the first flush device until it's full. Then, a plastic ball floats to the top of the device and directs the cleanest water to the tank.

Meanwhile, a flow restrictor at the bottom of the first flush device slowly releases the dirty water to 'reset' the device for the next rainfall. This flow restrictor is really the only component that needs regular attention. They often block with debris and dirt and need to be cleaned after each heavy rainfall event.

If you don't regularly clean your flow restrictor, the device will remain full of dirty water which will soon become stagnant. When the device is full, it won't be able to catch the next 'first flush' of dirty water.

How do you clean your first flush device?

  1. Simply unscrew the bottom of the first flush device. Take care to avoid being splashed by dirty water as it rushes out!

  2. Rinse out the bottom cap that you unscrewed (and all its components) with fresh water.

  3. Reassemble everything as you found it.


Your device is now ready for the next big rain event and you can be sure only the cleanest water is entering your tank.

Mains switching devices,  are designed to fail 'safe'.

This means you'll continue to receive water from the drinking water supply when your tank is empty or your pump has stopped.

Sometimes mains switching devices fail due to an electrical storm or blackout. You'll need to manually reset them.

Be sure to check your owner's manual, or manufacturer's instructions so you know the difference between the failed and operating status of your swiching device.

Regularly check your switching device to make sure it's operating normally. That way you're making the most of your rainwater supply.