Boiler Pressure Too High
Your boiler's pressure gauge should read between 1.0 and 1.5 bar when cold. If it consistently reads above 2.0 bar — especially when the boiler is heating — you have a high-pressure fault that needs attention. High system pressure stresses joints, seals, and the expansion vessel, and will eventually trigger the pressure relief valve to discharge.
Common causes include a failed expansion vessel (lost its air charge), overfilled filling loop, or a leaking filling valve allowing mains water to constantly enter the system. Our licensed technicians diagnose the root cause quickly — often fixing the issue same-day.
What Causes High Boiler Pressure
The most common cause is a failed expansion vessel — the internal diaphragm ruptures or loses its air charge, so there's no room for water to expand when heated. As water heats up and expands, pressure spikes. Other causes include the filling loop being left open or its valve passing water, or a leaking plate heat exchanger on combi boilers allowing mains water into the heating circuit.
How We Fix High Boiler Pressure
We check the expansion vessel air charge using a pressure gauge. If it's flat, we repressurize it (if the diaphragm is intact) or recommend replacement. We verify the filling loop is fully closed and not passing. We also check for heat exchanger cross-leakage on combi boilers. All work is quoted upfront with a fixed price.
This is not a DIY repair
Combi boilers are gas-fired appliances regulated under the BC Safety Standards Act. Opening the unit, touching the gas valve, or working on the flue without a valid BC gas-fitter licence is both unsafe and illegal. Diagnosing the fault is helpful — fixing it should always be left to a certified technician.
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