Quick answer
Turn the heating off, isolate the electrical supply to the boiler at the fused spur if it is safe to do so, place a container under the leak and call a Gas Safe registered engineer. Do not run the boiler while it is leaking. Water and electricity inside an appliance is a real risk, and a small leak left alone corrodes components and causes repeated pressure loss.
A leaking boiler is not something to monitor for a few weeks. Even a slow drip corrodes the case and the components underneath it, and it is the reason behind a lot of the repeated pressure loss calls we take.
What to do right now
- 1Turn the heating off at the programmer or thermostat.
- 2If it is safe and dry to do so, switch the boiler off at its fused spur.
- 3Put a container and towels under the leak to protect the floor and anything below.
- 4Do not remove the casing or try to tighten anything inside the boiler.
- 5Photograph where the water is coming from — it helps us bring the right parts.
- 6Call a Gas Safe registered engineer.
What the leak point usually tells us
| Where the water appears | Common cause |
|---|---|
| Below the boiler, clear water | Pipework joint, pump seal or a failed internal seal |
| From the pressure relief pipe outside | Pressure too high, or a failed expansion vessel or PRV |
| Around the base with staining | Long-standing slow leak — often the heat exchanger or a corroded fitting |
| Near the condensate connection | Blocked or split condensate pipe backing up |
| Rusty or brown water | Internal corrosion — usually a serious finding on an older boiler |
Leaks and pressure loss go together
If you have been topping the boiler up regularly, a leak somewhere in the system is the most likely explanation, even if you cannot see water. Our guide on a boiler that keeps losing pressure covers how we trace it.
Don't run a leaking boiler
Get it looked at properly — we diagnose the leak, tell you the cost, and only then start work.
Book a boiler repairWhen to call a professional
Safe homeowner checks stop at pressure gauges, radiator valves, controls and visible pipework. Anything involving gas, combustion, the boiler casing, the flue or internal components is work for a Gas Safe registered engineer. If you smell gas, follow the appropriate emergency gas safety guidance and do not attempt to work on the appliance.
Call 07881 963508The Betaflo recommendation
The safe immediate steps when a boiler leaks, what different leak points usually mean, and why leaks should never be left. If you'd like a second opinion before spending money, speak to us first — we'd rather tell you your boiler is fine than sell you something you don't need.
Frequently asked questions
Can I still use the heating if the leak is small?
We'd advise against it. Running a leaking boiler risks electrical components and makes the damage worse.
Is a leaking boiler dangerous?
Water inside an electrical appliance is a hazard in itself. It is not a gas emergency unless you can also smell gas — in which case follow emergency gas safety guidance immediately.
Why is water dripping from a pipe outside?
That's usually the pressure relief discharge, which means the system pressure went too high or the expansion vessel has failed. It needs investigating rather than ignoring.
About the author
Betaflo Heating UK
Betaflo Heating UK is founded and run by Miles Davis and Sam Boyle, Gas Safe registered heating professionals installing, servicing and repairing boilers across Tamworth, Birmingham and the surrounding areas. Our guides are written from the work we do in customers' homes every week. More about Betaflo.
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