Water & tank care
How to treat and clean a water tank
A rainwater tank quietly collects more than rain: leaf litter, dust, the odd bit of wildlife, and over time a layer of sediment on the bottom. Keeping it clean keeps the water better to use, and occasionally you’ll want to disinfect it. Here’s a plain-English rundown.
Keep the muck out first
The best treatment is stopping contamination getting in: a leaf guard or first-flush diverter on the inlet, a screened and sealed overflow and inlet to keep mosquitoes and animals out, and gutters kept clear. Cleaner water in means far less to treat.
Dealing with sediment
A slow build-up of sludge on the base is normal. It can be siphoned or pumped out, or the tank drained and cleaned every few years. Try not to stir the sediment up into the water you draw, and keep the outlet a little above the floor of the tank.
Disinfecting options
- Chlorine: the traditional approach, a measured dose to sanitise the water.
- Hydrogen peroxide: an alternative some prefer, because it breaks down to water and oxygen and leaves no lingering taste or smell.
- Both need to be dosed correctly for the volume of your tank. Too little does nothing, and too much is a problem.
Getting the dose right
Disinfecting a tank is all about matching the dose to the tank’s volume, and that’s where it pays to follow a proper guideline rather than guess. Australian health departments publish clear guidance on cleaning and disinfecting rainwater tanks, including dose rates. If the water is for drinking, or you have had contamination such as a dead animal, flood water, or an algal bloom, follow that guidance closely or get advice before you rely on the water again.
Safety: If your tank is your drinking supply and you suspect contamination, don’t drink it until it has been properly treated or tested. When in doubt, boil water for drinking or use an alternative supply, and seek advice from your local health authority.
Common questions
Hydrogen peroxide or chlorine for a tank?
Both work. Chlorine is the long-standing method; hydrogen peroxide appeals to people who don’t want any residual taste or smell, as it breaks down to water and oxygen. Whichever you choose, dose it to your tank’s volume using a proper guideline.
How often should I clean my tank?
Inspect it yearly, and plan a proper de-sludge every two to three years, sooner if you can see or taste a problem.