Boiler leaking water, what to do first

Do this first

Two minutes of the right actions saves a lot of damage.

• Turn the boiler off at the fused spur or isolator.
• Close the water supply valves under the boiler if you can reach them, or the internal stopcock if not.
• Put a bowl or towels under the drip and keep water clear of sockets and cables.
• Do not keep repressurising the system, you are only adding more water.
• Take a photo of where the water is coming from, it helps us bring the right parts.

Common causes

Where the water appears tells us a lot. Dripping from underneath is often pipework connections, a pump head seal or the diverter valve. Water from the pressure relief pipe outside points at an over-pressurised system or a waterlogged expansion vessel. Staining down the inside of the case is more often the heat exchanger or a failed seal.

Corrosion is the other one. Where a boiler has been quietly weeping for months, the internal components rust and the leak spreads from one component to the next.

What we do

We find the actual source, pressure test, and replace the failed component rather than sealing round it. Where the boiler is old and the leak is internal to the heat exchanger, we will tell you honestly whether a repair is worth the money.

Questions we get asked

Should I turn the boiler off if it is leaking?

Yes. Switch it off at the fused spur, isolate the water supply to it if you can reach the valves, and put a container under the leak. Keep water away from any electrics.

Can I keep topping the pressure up?

No. Repressurising a boiler that is losing water just pushes more water into your house and hides the fault. Get the leak found first.

Is a leaking boiler always a replacement?

No. Most leaks are a seal, a valve, a pump head or corroded pipework rather than the boiler body. Where the heat exchanger itself has gone on an older unit, replacement usually makes more sense, and we will show you why.