How a rainwater tank is plumbed
Every tank follows the same path. Once you can name each part, faults get much easier to read.
A rainwater tank is plumbed in one line: roof, gutter, screen, first flush diverter, tank, pump, house. Overflow leaves the tank by its own pipe. Learn that order and a plumbing diagram stops looking like a maze.
The path from roof to tank
Rain lands on the roof and runs into the gutters. Leaf guards or gutter screens catch the big debris first. From there the water drops into downpipes that lead to the tank.
Before it reaches the tank, many systems send the first dirty water to a first flush diverter. Then the cleaner water goes in through a screened inlet. That screen keeps leaves and mosquitoes out.
What happens inside and around the tank
The tank stores the water. A good one has a sealed lid, a screened inlet and a screened overflow pipe. The overflow takes surplus water away from the tank and from the house footings.
Some tanks have a mains top-up. A float valve lets mains water in only when the tank runs low. It must be fitted so mains water can never be drawn back from the tank. That is a backflow rule, and licensed plumbers deal with it.
From the tank to the house
A pump pushes water out of the tank and into the pipework. A filter usually sits on the suction side to protect the pump. Pressure then carries the water to the toilets, the laundry and the garden taps.
Some homes also feed the hot water system or the kitchen tap. That is where the rules get strict, because the water quality and the plumbing standards both matter.
| Part | What it does | Who handles the job |
|---|---|---|
| Gutter and leaf screens | Stop large debris reaching the tank | You can clear them from a safe position |
| First flush diverter | Discards the dirtiest first water | You can empty it, a plumber fits it |
| Inlet and overflow screens | Keep out leaves, insects and animals | You can check them |
| Mains top-up and float valve | Adds mains water when the tank is low | Licensed plumber |
| Pump and suction filter | Pressurises the supply to the house | Licensed plumber and licensed electrician |
| Connection to house plumbing | Delivers tank water to fixtures | Licensed plumber |
Using a diagram to find a fault
Work backwards from the symptom. No water at the taps with a full tank points at the pump or its filter. Dirty water points at the inlet screen and the diverter. Water pouring out of the tank when it has not rained points at a stuck float valve.
Take a photo of your own setup and label each part. It helps a plumber diagnose a problem faster, and it helps you spot what has changed.
Symptom to part: where to look first
Work backwards from what you see. This table points at the part to check before you call anyone.
| Symptom | Part to look at | Who handles it |
|---|---|---|
| No water at the taps, but the tank is full | Pump or its suction filter | Licensed plumber and licensed electrician |
| Dirty water | Inlet screen and the first flush diverter | You can check them, a plumber fits a diverter |
| Water pouring out when it has not rained | Float valve, which may be stuck | Licensed plumber |
| Mosquitoes or leaves in the tank | Screened inlet and screened overflow | You can check the screens |
| Water running along the footings | Overflow pipe route | Licensed plumber or your council |
| Tank empty in a dry spell | Mains top-up, if you have one | Licensed plumber |
Our guides to the float valve and tank pumps go deeper on the two most common culprits.
Map your own tank in ten minutes
A labelled photo of your setup helps a plumber diagnose a problem faster, and it helps you spot what has changed.
- Start at the roof. Note whether you have leaf guards on the gutters, and where each downpipe goes.
- Follow the downpipe to the tank. Look for a first flush diverter on the way, and note whether there is one.
- Find the inlet. Check that it has a screen, and photograph it.
- Find the overflow. Follow it to where the water goes, and make sure it leaves the tank and the house footings.
- Look for a mains top-up and float valve. If you have one, photograph the connection but do not touch it.
- Follow the pump line to the house. Photograph the pump, the filter and where the pipe enters the house.
Label each photo with the part name, and keep them with your warranty papers. Cutting into any pipework or wiring is licensed work.
Frequently asked questions
What is the correct order of rainwater tank plumbing?
Roof, gutter, screen, first flush diverter, tank, pump, then the house. The overflow leaves the tank by a separate screened pipe.
Where does the overflow pipe go?
It should carry surplus water away from the tank and house footings, to a stormwater connection or a safe discharge point. Your state or local council sets the rules.
Can I connect a rainwater tank to my house myself?
No. In Australia that work needs a licensed plumber, and the rules differ by state and territory.
Why does a tank need a screened inlet?
The screen keeps leaves, insects and mosquitoes out of the stored water.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Australian Building Codes Board. National Construction Code — Volume Three (Plumbing Code of Australia)