Leak triage

Water leaking from the boiler: what is urgent and what can wait

Water and electricity in the same casing is the reason boiler leaks deserve prompt attention. The first job is to work out whether it is a fitting, a component, or the heat exchanger itself.

Written for: Anyone who has found water under the boiler
Water damage beneath a wall-hung boiler

Practical notes on a leaking boiler

  • Turn the appliance off and place a container under the drip
  • Photograph where the water emerges before wiping it up
  • Relief valve leaks are usually an expansion vessel issue
  • Heat exchanger corrosion is terminal on most older boilers
  • Wet electrics inside the case make it an isolate-now job

Who should undertake the work

  • Gas appliance work must be completed by a suitably qualified Gas Safe engineer
  • Oil appliance work should be completed by a suitably qualified OFTEC technician
  • Jamie Crawford Heating states both Gas Safe and OFTEC registration

Where a leaking boiler usually comes from

Leaks from pipework connections under the appliance are usually repairable in a single visit. Leaks from the pressure relief valve are a vessel conversation. Leaks from the condensate trap are messy but low risk. Water from inside the sealed casing, particularly from a corroded heat exchanger, is where replacement economics start to matter on older appliances.

Where we deal with this

Straight answers on a leaking boiler

Our advice: Photograph the source, isolate the appliance, then get it diagnosed before water finds the electrics.

Include the appliance make and model in your enquiry so the correct technical information can be checked.

Questions we get asked

Should I turn the water off?
Isolate the boiler electrically and, if it is a combi, close the cold mains inlet if the leak is on the water side.
Will my warranty cover it?
If the appliance is in warranty and has been serviced annually, usually yes — keep your service records.

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