We are about to let our house and the landlord's gas safety test has detected a fault. When the system is shut off from the main the pressure after at meter drops by about 0.01 mB per second. I think the pressure was around 20 mB. It was a digital meter.
Now, the first puzzle is that BG and another plumber both passed the pressure test a year ago when the meter was moved and some pipwork rerouted. Nothing has been done to the gas system since then.
The second puzzle is that he said that when he measured it, the pressur "held OK for a bit and then started to drop".
The house has a mix of copper and old iron gas pipes, all are capped except at the boiler. It's a 3 bed end terrace.
Any thoughts?
. Robert