Why Does Pressure Rise When the Heating Comes On?
Water expands as it heats, so some movement on the pressure gauge is expected. The boiler and heating system are designed to accommodate that change.
A very large increase, however, should be investigated.
Was the System Recently Repressurised?
If too much water was introduced when topping up the system, the starting pressure may already be higher than intended.
Always follow your boiler manufacturer's instructions rather than using a pressure figure from another boiler model.
Expansion-Vessel Problems
The expansion vessel helps accommodate the change in water volume as the heating system warms. A fault affecting this process can contribute to larger-than-normal pressure fluctuations.
High When Hot, Very Low When Cold?
If pressure rises sharply during heating and then falls excessively after cooling, this pattern can be useful information for an engineer.
See our broader guide to a boiler losing pressure.
Is Water Also Leaking?
If you notice water near the boiler or pipework, read boiler leaking water in South Ockendon.
Boiler Pressure Rising Too High?
Boilers 4 Essex can diagnose pressure and expansion problems throughout South Ockendon.
Frequently Asked Questions
Should boiler pressure rise when heating?
Some increase is normal as system water warms, but an unusually large rise can indicate a problem.
Can high pressure damage a boiler?
The system has protective components, but persistent abnormal pressure should be diagnosed rather than ignored.
