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Combi boiler dropping to zero bar: a hidden hallway leak in Market Deeping
A combi boiler kept losing pressure after multiple visits had found no fault. A careful air test proved a small leak, a damp meter led to one spot in the hallway, and the floor there held a leaking 15 mm pipe inside a plastic sleeve.
What was happening
The combi boiler gauge read zero bar when the engineer arrived. The system had been losing pressure repeatedly, and several earlier engineer visits had found no fault. Part of the hallway floor had already been disturbed, and a slight damp spot remained there.
What the engineer did
The heating was drained and the water left in the pipes was vacuumed out so an air test would be clean. The first test showed no drop. After more vacuum cycles, a very small but measurable drop showed over 30 minutes, which proved there was a live leak. Tracer gas found nothing at the surface, and thermal imaging showed only some unclear marks in the floor. A damp meter gave its maximum reading of 999 at one spot in the hallway.
What was found
With the customer's agreement, the already disturbed part of the floor was opened further. Beneath it was a leaking 15 mm heating pipe inside a plastic cover, which explained why no tracer gas had reached the surface. The ground around it was heavily saturated, consistent with a leak that had been running for several months.
What happened next
A new section of 15 mm copper pipe and fittings was fitted and wrapped with protective tape. The engineer advised drying the floor thoroughly before it is re-screeded and tiled, and flushing the heating system, which was found to be very dirty.
If your boiler is doing the same
When one method comes back blank, it does not mean there is no leak. Here the pressure test proved a leak, the tracer gas was blocked by a plastic sleeve, and the damp meter found the spot. If you have had engineers out and the pressure is still going, a survey that uses several methods is the next step.
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Pressure falling too fast to run the heating
The pressure fell so quickly the heating could not run. Tracer gas, a damp meter and a microphone all pointed to the same spot in an outbuilding floor. The sandstone slabs came up without breaking, and a pinhole in a corroded pipe was repaired and pressure tested.