Why your rainwater tank pump is not working
Start with the tank level and the power. Most dead pumps are one of those two.
When a tank pump stops, the pump itself is often fine. Check the water level in the tank, then the power, then whether the pump has lost its prime. Only after that is it worth suspecting the pump.
Work out which fault you have
The symptom narrows the cause fast. Listen to the pump before you touch anything.
| What you notice | Likely cause | What to look at |
|---|---|---|
| Silent, no hum | No power, or a tripped safety switch | The switchboard and the pump indicator |
| Hums but does not pump | Seized impeller or a blocked inlet | Have it checked; do not keep it running |
| Runs but delivers little | Lost prime, blocked strainer or low tank | Tank level, strainer, suction side joints |
| Starts and stops repeatedly | Short-cycling from a leak or a low air charge in the pressure vessel | Taps, toilet cisterns and outlet joints |
| Worked, then died after a dry spell | Ran dry and damaged the seals | Tank level history and low-level protection |
Check the tank before the pump
A tank that looks full from the lid can be empty at the outlet. Check the level properly. If the tank is low, the pump may be drawing air, and that is not a pump fault.
Also check that the outlet tap on the tank is open and the strainer is clear. Leaves and sludge block a strainer more often than a pump fails.
Prime problems and air leaks
A surface pump has to be full of water to work. Any small leak on the suction side lets air in, and the pump loses prime. It then runs, makes noise and moves very little.
Look for damp fittings and drips on the pipe between the tank and the pump. A joint that weeps air does not always weep water.
Short-cycling means something is bleeding pressure
If the pump starts and stops while nothing is running, pressure is leaking away somewhere. A running toilet cistern is a common culprit. So is a dripping tap or a pressure vessel that has lost its air charge.
Turn off every outlet and watch the pump. If it still cycles, the leak is somewhere you cannot see. Leave the diagnosis to a plumber. A pump that cycles for weeks wears out early.
Do not run a dry pump to test it
Seals cook within minutes without water. If you suspect the tank is empty, switch the pump off. A low-level cut-out is the fix most systems are missing. Our guide to tank pump types and why they fail covers the options.
A five-minute check before you call anyone
These checks are safe for an owner. Stop as soon as you reach pipework or wiring.
- Check the tank level. A tank that looks full from the lid can be empty at the outlet.
- Check the outlet tap. It must be open on the tank.
- Look at the strainer. Leaves and sludge block it more often than a pump fails.
- Check the switchboard. Look for a tripped switch and the pump indicator.
- Listen. Silent, humming and running-but-weak each point somewhere different.
- Do not run it dry. If the tank may be empty, switch the pump off.
After that, call a licensed plumber or licensed electrician, depending on the fault.
Who to call for each pump fault
| Fault | Call | Why |
|---|---|---|
| Silent, power seems off | Licensed electrician | Pump wiring and safety switches are electrical work |
| Hums but does not pump | Licensed plumber or pump specialist | A seized impeller or blocked inlet needs checking; do not keep it running |
| Runs but delivers little | You first, then a licensed plumber | Check level and strainer, then the suction side joints |
| Cycles with nothing running | Licensed plumber | Pressure is leaking somewhere you cannot see |
| Died after a dry spell | Pump specialist | The seals may be damaged |
| Connections to house or toilets | Licensed plumber | Backflow prevention is involved |
Our guide to pressure pumps for a house explains the pressure vessel and why it affects cycling.
Frequently asked questions
Why is my rainwater tank pump running but no water coming out?
The usual causes are a low tank, a blocked strainer or lost prime from an air leak on the suction side. Check the tank level first and switch the pump off if it is empty.
Why does my tank pump keep starting and stopping?
Pressure is leaking away or the pressure vessel has lost its air charge. A running toilet cistern or a dripping tap is a common cause.
Can I repair a tank pump myself?
You can check the level, the strainer and the switchboard. Wiring is electrician work, and connections to house plumbing are licensed plumbing work.
Will running a pump dry damage it?
Yes. Seals can fail within minutes without water, so switch the pump off if the tank may be empty.
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)