Why does the pressure drop on my Combi boiler hot water and central heating system ?
There are four possible causes for the pressure drop in your system – 1/ A leak, it is unlikely that the drip on your radiator would cause such a dramatic pressure drop 2/ The pressure relief valve letting-by – there will be an open ended pipe that goes from your boiler through the wall to outside, check that this isn’t dripping/running 3/ The expansion vessel losing it’s pressure – the system would have to be drained down and the pressure in the expansion vessel checked 4/ Air in the system venting through the automatic air vent in the boiler It will be one of these problems, only investigation will determine which one.
