Boiler Leaking Water London — Causes, Signs & Fixes

Faulty pressure relief valve

The most common source of boiler leaks. The PRV opens to release excess pressure — if it weeps continuously, it needs replacing. Usually a quick fix.

Corroded or cracked heat exchanger

The heat exchanger transfers heat from gas to water. Corrosion or hairline cracks cause internal leaks. This is a more significant repair but our engineers carry heat exchangers for most premium brands.

Loose or degraded pipe fittings

Compression fittings and push-fit joints inside the boiler casing can work loose over years. Tightening or replacing takes minutes once the casing is off.

Pump seal failure

The circulating pump has a mechanical seal that can fail, particularly in boilers over 8 years old. Causes water around the pump housing.

Leaking diverter valve (combi boilers)

The diverter valve splits flow between heating and hot water. A failing O-ring causes internal leakage into the heat exchanger.

Is a leaking boiler an emergency?

Yes — turn the boiler off and call an engineer the same day. Water dripping onto electrical components inside the boiler is a fire and electric shock risk. Even a slow drip can cause structural damage over time.

Can I still use my heating if the boiler is leaking?

No. Turn the boiler off until an engineer has assessed it. Running a leaking boiler risks further damage and potential safety hazards.

How much does it cost to fix a leaking boiler?

Depends on the cause. Replacing a PRV or seal is a straightforward repair. A cracked heat exchanger is more involved. RARE provides fixed pricing before any work begins — call us for a quote.

My boiler is leaking from the bottom — what does that mean?

Leaks from the bottom of the boiler most commonly indicate a faulty PRV drip pipe, a failing pump seal, or condensate pipe issues (on condensing boilers). All are repairable on the same visit.