Minor pressure increases are common after the heating has been running.
Common situations
Action
Continue monitoring the pressure gauge.
Pressure that remains high may indicate a developing fault.
Common signs
Action
Arrange an inspection if the problem continues.
Very high pressure can damage your heating system.
Warning signs
Action
Switch the heating off and contact a Gas Safe engineer.
Contact a Gas Safe engineer if:
High boiler pressure is commonly caused by an overfilled heating system, a faulty filling loop, a failed expansion vessel or a problem with the pressure relief valve. While small pressure increases are normal when your heating is running, pressure that remains consistently high should be investigated to prevent damage to your boiler.
A pressure reading of around 2.5 bar while the heating is running isn't always a cause for concern. However, if the pressure remains at this level when the system is cold or continues rising towards 3 bar, it's recommended to have your boiler inspected.
Most boilers are designed to release excess pressure automatically through the pressure relief valve when the pressure exceeds approximately 3 bar. This may cause water to leak from the boiler. Repeated high pressure can place unnecessary strain on the heating system and should be investigated by a Gas Safe engineer.
Yes. If left unresolved, excessive pressure can damage seals, valves and other internal components. It may also trigger boiler lockouts or cause water to discharge through the pressure relief valve. Resolving high pressure early helps avoid more expensive repairs.
Pressure that repeatedly rises usually indicates an underlying fault rather than a one-off issue. Common causes include a faulty filling loop that continues adding water, a failed expansion vessel or a defective pressure relief valve. If your pressure frequently climbs without explanation, it's best to arrange a professional inspection.
In some situations, excess pressure can be reduced by carefully bleeding a radiator or releasing a small amount of water from the system, provided you follow your boiler manufacturer's guidance. If the pressure quickly rises again, avoid repeatedly lowering it and arrange an inspection, as there may be a fault that requires repair.
A pressure relief valve often leaks because the system pressure has become too high. If the valve continues leaking even after the pressure returns to normal, the valve itself may be worn or damaged and may need replacing. Persistent leaks should always be checked by a Gas Safe engineer.
Yes. Keystone provides boiler pressure diagnostics and repairs throughout London. Our experienced Gas Safe engineers identify the cause of both high and low pressure problems, repair faulty components and restore your heating system to safe working condition.
The cost depends on the cause of the problem and whether replacement parts are required. Some issues can be resolved with simple adjustments, while others involve repairing or replacing components such as the expansion vessel or pressure relief valve. Keystone provides transparent quotations after diagnosing the fault, so you'll know exactly what's required before any work begins.
Keystone provides trusted boiler repair services across London, helping homeowners resolve pressure problems quickly and safely. Our Gas Safe engineers diagnose faults efficiently, explain the cause clearly and provide transparent pricing before carrying out any repairs. Whether your boiler pressure is too high, too low or fluctuating unexpectedly, we're here to help restore your heating with reliable, long-lasting solutions.