Boiler Pressure Too High
The gauge sits well above 2.5 bar when hot, and water occasionally discharges from a pipe outside..
The gauge sits well above 2.5 bar when hot, and water occasionally discharges from a pipe outside.
What is actually going on
The gauge sits well above 2.5 bar when hot, and water occasionally discharges from a pipe outside.
The realistic causes, in order
A filling loop left open, or a filling valve passing slightly, continuously adding mains water A waterlogged expansion vessel with no air cushion left to absorb expansion A failing plate heat exchanger letting mains pressure cross into the sealed heating circuit
What we test on site
Cold and hot pressure readings taken twenty minutes apart to see how far the system swings Vessel pre-charge with the system depressurised, re-charged to the manufacturer's figure if the diaphragm is intact The filling loop for passing, by isolating it and re-testing
Questions we get asked
What causes boiler pressure that climbs too high on a gas boiler?
A filling loop left open, or a filling valve passing slightly, continuously adding mains water
What normally puts boiler pressure that climbs too high right?
Recharging or replacing the expansion vessel resolves most cases and stops the relief valve wearing out.
Is it safe to keep using the system with boiler pressure that climbs too high?
Do not repeatedly bleed radiators to control high pressure. That removes system inhibitor and hides the real fault.