Pressure keeps dropping
The boiler loses pressure after being topped up and needs repeated attention.
Heating Leak Symptom
Boiler Losing Pressure
Boiler pressure can fall for several reasons, from recently bled radiators and visible valve leaks to boiler faults or concealed heating pipework loss.
A pressure reading does not prove that a concealed leak exists. The pattern, visible signs and recent work on the system help determine the appropriate next step.
- Central Heating Leaks
- UFH Leak Detection
- Non-Destructive Methods
Causes
What Causes This Problem?
The underlying cause is not always visible. A structured investigation helps separate surface symptoms from the source of water escape.
Radiators recently bled or system recently drained
Radiator valve or fitting fault
Pressure relief valve discharge
Boiler component or expansion vessel fault
Hidden central heating pipe leak
Underfloor heating circuit or manifold leak
Signs
Common Signs
Heating performance changes
Radiators or heating zones may become unreliable when system pressure falls.
Damp floor areas
Moisture or staining may appear away from the actual heating pipe leak.
UFH zones not heating
Underfloor heating loops may lose performance if a concealed leak is present.
Repeated top-ups
Regularly repressurising the system can point to an unresolved fault.
Pressure falls with no visible source
Dry radiators and accessible pipework do not rule out a boiler fault, intermittent loss or concealed heating pipe leak.
Timing
When To Investigate
Pressure loss repeats or accelerates
A one-off change may follow recent system work, but recurring or rapid loss should be assessed rather than managed with repeated top-ups.
Damage is appearing
Damp, staining or flooring changes should be investigated before repairs are started.
Water is escaping or the boiler locks out
If water is actively escaping, electrical safety may be affected or the boiler repeatedly locks out, stop routine checking and seek appropriate qualified help.
Insurance evidence is needed
Written findings and photographs can support escape of water or trace and access claims.
Investigation
How Leak Detection Helps
Locates hidden pipework
Specialist methods help narrow the likely leak position before access work.
Reduces unnecessary damage
Investigation is carried out before floors or finishes are removed unnecessarily.
Supports repair planning
Clear findings help heating engineers target the correct area for repair.
Related Services
Recommended Leak Detection Services
Useful Links
Related Guidance And Evidence
Related Investigations
Related Investigations
Published case studies linked to this symptom or problem.
Thames Ditton, Surrey
Underfloor Heating Leak Detection in Thames Ditton
Underfloor Heating Leak
A plumber identified pressure loss on an underfloor heating circuit in Thames Ditton; combined testing narrowed the issue to an area beneath the wood flooring.
View investigation
Woking, Surrey
Boiler Pressure Loss Investigation in Woking
Central Heating Leak
Boiler pressure loss in Woking traced and repaired in a single visit, reducing disruption for the customer.
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Knightsbridge, London
Central Heating Leak Detection in Knightsbridge
Central Heating Leak
Boiler issue in Knightsbridge diagnosed as a concealed leaking pipe beneath garden slabs and resolved for the landlord.
View investigationFAQs
Boiler Losing Pressure FAQs
Why does my boiler keep losing pressure?
Repeated pressure loss can follow recently bled radiators or be caused by a visible valve leak, pressure relief discharge, expansion vessel or other boiler fault, underfloor heating loss or a concealed heating pipe leak.
Can a hidden leak cause boiler pressure to drop?
It can. A small leak in central heating pipework may cause ongoing pressure loss even when no water is visible, but pressure loss alone does not prove that a concealed leak exists.
Can you find heating leaks without lifting floors?
Non-destructive methods are used first, including thermal imaging, tracer gas and moisture mapping where suitable.
Is underfloor heating pressure loss different?
Underfloor heating leaks can be harder to see because pipework is concealed beneath flooring or screed, so specialist detection is often needed.
Can findings support an insurance claim?
Written findings and photographic evidence may support discussions with an insurer or loss adjuster where these are included in the agreed investigation. The insurer decides whether the policy responds.
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