In short
- If the water is close to electrical connections or a socket, unplug the boiler first.
- Look at the pressure gauge; if the pressure is very high, the pressure relief valve may be letting out water.
- On condensing boilers, the condensate pipe may have come loose or become blocked.
What to do first
- If the water is close to a socket, cables or the electrical connection under the boiler, unplug the boiler or switch off its circuit breaker.
- Put a container under the drip and look at where the water is coming from.
- Look at the pressure gauge and write down the reading.
Possible causes
- The pressure relief valve is letting out water: When the pressure gets close to 3 bar, the valve opens and lets out water. If the pressure rises a lot when the boiler heats up, the expansion vessel may have weakened or too much water may have been added to the system.
- Condensate pipe: Condensing boilers produce water while they run, and this water flows down a pipe into the drain. If the pipe has come loose, been crushed or become blocked, water drips under the boiler. Pipes that run outside can freeze in cold weather.
- Leaking connections: At the pipe connections under the boiler, a seal may have worn out or a fitting may have come loose.
- Leak inside the boiler: Water from the heat exchanger, the pump or the internal connections drips out from under the boiler. Only a technician can see this, by opening the cover.
When should you contact a technician?
If the water is coming from inside the boiler, if the pressure relief valve often lets out water, or if the pressure keeps dropping, the boiler should be inspected. If only the condensate pipe has come loose, putting it back in place may be enough; if you are not sure, take a photo and send it to us on WhatsApp, and we'll explain what to do.
Dereli Teknik · 25 September 2026