In many villas that rely on a water tank, the water pressure comes from a booster pump (known locally as a hidrofor). Normally, the pump starts when a tap is opened and stops shortly after it is closed. If the pump runs while nobody is using water, or keeps switching on and off at short intervals, something is wrong with the system. It pushes up your electricity use and shortens the pump's life.
First, describe what the pump is doing
Whether you're explaining the problem to a plumber or checking it yourself, it helps to note how the pump behaves:
- It runs non-stop: The pump may not be reaching the required pressure.
- It starts and stops at short intervals: If it kicks in every few minutes with all taps closed, there may be a leak or a problem with the tank.
- It switches on and off very rapidly when a tap is open: The air pressure or the membrane of the pressure tank may be at fault.
Possible causes
1. A leak in the system
This is one of the most common causes. If a tap, a cistern, a buried pipe or a garden line is leaking, the pressure drops and the pump starts to make it up. To check for a leak, you can use the methods in the guide on signs of a hidden water leak and the meter test; in a system with a booster pump, check the cisterns and the garden line in particular.
2. A leaking check valve (non-return valve)
The check valve stops water flowing back into the tank when the pump stops. If it doesn't close fully, the pressure slowly falls and the pump starts on its own.
3. Low air pressure or a torn membrane in the pressure tank
The membrane tank holds a reserve of water under pressure, so the pump doesn't have to start for every small draw of water. The air pressure in the tank can drop over time. If the membrane tears, the tank fills with water and can no longer do its job. The pump then switches on and off very often. The correct air pressure depends on the pump's settings, and it should be measured with the pump switched off and the water pressure released.
4. Pressure switch setting or fault
The pressure switch decides at what pressure the pump starts and stops. If it is set wrongly or faulty, the pump cannot reach the pressure at which it should stop.
5. Air on the suction side or a low tank
An air leak in the suction pipe, a blocked strainer or a low water level in the tank makes the pump work inefficiently. A pump running with an empty tank runs dry and can be damaged quickly.
What you can do
- Close all taps and watch whether the pump starts on its own.
- Look for leaks at the cisterns, the garden line and any visible connections.
- Check the water level in the tank.
- If the problem continues, switch off the pump's power and have a plumber check it.
Safety: A booster pump combines electricity and water. Switch off the power at the fuse box before touching the pump, the pressure switch or its connections. There is live voltage under the pressure switch cover; it is dangerous for anyone unqualified to open it. Before removing a pressure tank or pipes, the pressure in the system must be released.
Frequently asked questions
Is it dangerous for the pump to run constantly? Constant strain can overheat the motor and shorten its life. Running with an empty tank can damage the pump quickly.
Should I switch the booster pump off when I leave the house? If you'll be away for a long time, closing the main stopcock and switching off the pump's power stops a possible leak from getting worse. For details, see the guide on winterising an empty house.
What is dry-run protection? Some systems have a safeguard that stops the pump when the tank runs out of water. You can ask a plumber whether your system has one.
For booster pump servicing and fault finding, see the plumbing page.
This guide is for general information. Every home is different; for your own home, ask a company that has seen the work on site for a written quotation.