Looking after your rainwater tank: a homeowner's guide

A rainwater tank is one of those things that works quietly in the background until it doesn't. Then the toilets stop filling, the pump won't stop running or the toilet bowls turn brown. Nearly every one of those problems starts with a tank that hasn't been looked after. This guide explains how a typical home tank system works, what goes wrong, and the simple checks that keep it running. It's written by the licensed plumbers who look after tanks and pumps across the southern Eastern Suburbs.

How a home rainwater system works

Rain runs off the roof into the gutters and down the downpipes. On the way to the tank it should pass through a leaf screen or rain head, and often a first flush diverter, which holds back the dirtiest water from the start of each storm. The tank fills, and any extra water leaves through the overflow into the stormwater system.

A pump draws water from the tank and pushes it to the toilets, laundry and garden taps. Most systems also have a changeover device that switches to mains water when the tank runs low, so the toilets still work in a dry spell.

What goes wrong

A simple maintenance checklist

NSW Health advises clearing roof gutters every three or four months, keeping screens clean, and checking tanks for sludge at least every two to three years. Here's what that looks like in practice:

• Every season: clear the gutters, clean the leaf screens and rain heads, and empty the first flush diverter.
• Before storm season: trim branches hanging over the roof and check the downpipes and overflow are clear.
• Once a year: check the insect screens on the inlet and overflow are sealed and undamaged, and look for cracks or gaps in the tank and lid.
• Every two to three years: have the sludge level checked and the tank cleaned out if needed. Have the pump, pressure switch and changeover device checked at the same time.
• If you have a filter: change the cartridge as often as the maker recommends, or sooner if pressure drops.

Please don't climb into a tank to clean it. Tanks are confined spaces, and the job is safer done from outside with the right equipment.

Upgrades that make a real difference

• Inline sediment filter: fitted after the pump, it catches fine grit before it reaches the toilets and laundry.
• Floating intake: draws water from just below the surface, where it's cleanest, instead of from the sludge on the floor.
• First flush diverter: keeps the dirtiest roof water out of the tank.
• Better leaf screens: stop most of the leaves and debris before they reach the tank.

See our rainwater tank maintenance page for how we clean tanks, fit filters and repair pumps.

Rainwater tanks in southern Eastern Suburbs homes

Plenty of newer and rebuilt homes in Pagewood, Eastgardens, Matraville and Little Bay have a slimline tank down the side path or a tank under the deck. Near the coast in Maroubra and Malabar, roofs collect salt and sand; under the big street trees in Kingsford and Matraville, gutters fill with leaves. Either way, it all ends up in the tank unless it's caught on the way.

In town, tank water is best kept for toilets, laundry and the garden. NSW Health recommends using mains water for drinking and cooking where it's connected.

Related help: rainwater tank maintenance, water filters, stormwater guide and blocked downpipes. Local pages: Pagewood, Eastgardens, Kingsford and Malabar. Browse all our plumbing guides.