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Boiler losing pressure with no damp anywhere: a faulty relief valve in Bracknell
The homeowner was recharging the boiler constantly, yet nothing inside was wet. The water was leaving through the pressure relief valve outlet on an outside wall. The engineer replaced the valve and a passing radiator valve on the same visit.
What was happening
The boiler sits in the loft, and the homeowner had been recharging its pressure again and again. The gauge read 1 bar when the engineer arrived. With no stains, no damp and no water-damaged areas anywhere in the property, there was nothing to point at, which is exactly why it needed a structured survey.
What the engineer did
Thermal imaging traced the heating pipework through the house and found no warm spread anywhere. Moisture mapping across the property found no raised readings either. The engineer then looked at the pressure relief valve outlet and saw water escaping there. To prove it, the system was drained and tracer gas was fed in through the main bedroom radiator at 1 bar. Gas came out at the relief valve outlet.
What was found
The relief valve was the fault. With its outlet pipe cut and capped, the system held pressure at 1 bar for 30 minutes and at 2 bar for 45 minutes, so the pipework itself was sound. The thermostatic valve on the front door radiator was also found to be passing.
What happened next
A new pressure relief valve was fitted, and the thermostatic valve on the front door radiator was replaced at the same visit. The engineer recommended keeping an eye on the gauge to confirm the system holds.
If your boiler is doing the same
No damp does not mean no leak. Before anyone lifts a floor, find the small pipe that comes out of the boiler and through the wall, and look under its end for drips, a wet patch or a limescale mark. If the pressure is going and the house is dry, that is the first place to look.
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