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Fix your leaking boiler.
What to do now (turn it off), what it usually costs to repair, and when a leak means a new boiler.
✓ Updated May 2026✓ Free quotes✓ Vetted pros
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Discovering leak late
— ceiling damage from upstairs boiler.
Repeated PRV leak
— expansion vessel needs attention.
Boiler beyond economic repair
— heat exchanger replacement vs new boiler comparison.
Costs & timeline
Know what it costs. Know when it ends.
Indicative UK ranges and what affects price.
Cost range
By job type
Inc. VAT · 2026
Source: NMT quotes
Source: NMT quotes
PRV replacementOften the leak point
£120–£300
Pump replacementMajor component
£250–£500
Auto air ventQuick repair
£120–£280
Pipework joint repairAccess dependent
£120–£400
Expansion vesselCommon older boilers
£250–£500
Heat exchangerOften replace boiler instead
£800–£2k
!
Quote spread is typically ± 18% — always get 3 quotes.
At a glance
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A leaking boiler is serious — water damage spreads, electrical issues become possible, and underlying causes can be expensive. This guide covers what to do immediately, common leak causes, and what UK boiler leak repair costs in 2026.
Immediate Steps
- Turn off boiler at the electrical supply.
- Turn off cold water inlet to boiler if you can locate it.
- Open a tap to relieve any pressure.
- Place towels/bucket to contain water.
- Call a Gas Safe engineer.
Common Leak Sources
- Pressure Release Valve (PRV) — over-pressure dripping. Usually expansion vessel.
- Pump seal — old pump leaks at seal.
- Heat exchanger — internal failure, serious.
- Pipework connections — older joints failing.
- Auto air vent — leaking from top of boiler.
- Expansion vessel — internal corrosion.
Typical Repair Costs
| Issue | Low £ | High £ | Notes |
|---|---|---|---|
| PRV replacement | 120 | 300 | Often the leak point |
| Pump replacement | 250 | 500 | Major component |
| Auto air vent | 120 | 280 | Quick repair |
| Pipework joint repair | 120 | 400 | Access dependent |
| Expansion vessel | 250 | 500 | Common older boilers |
| Heat exchanger | 800 | 2,000 | Often replace boiler instead |
UK Regulations
- Gas Safe Registration required for repair.
- DIY repair is illegal for gas-related components.
Common Problems
- Discovering leak late — ceiling damage from upstairs boiler.
- Repeated PRV leak — expansion vessel needs attention.
- Boiler beyond economic repair — heat exchanger replacement vs new boiler comparison.
Frequently Asked Questions
Is a leaking boiler dangerous?
Yes — water + electrical components is dangerous. Turn off immediately.
Why is water dripping from underneath?
Most common: PRV releasing over-pressure. Less common: pump or expansion vessel.
When should I replace vs repair?
If repair cost > 50% of new install, replace. If boiler over 12-15 years, also lean to replace.
What if water came from above?
Could be radiator, pipework, or upstairs unit. Find the source before treating.
Will insurance cover it?
Sudden/accidental damage may be. Gradual deterioration usually not. Check policy.
How urgent is repair?
Same day or next day. Don't run a leaking boiler.
This guide was written with AI assistance and is intended for general information only. Prices are estimates based on UK averages and may vary by region. Always get at least three quotes and consult a qualified professional before starting any work.
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