Originally Posted by pegmosaic
mine did that, I had a leak under a tiles floor!! :-(
A leak outside of the boiler, ie in any of the pipes below/above the boiler, will NOT make the pressure release valve (PRV) discharge.
Gauge rises from its normal 1bar to 2.5bar (at which point the safety valve kicks in) mainly due to:
faulty filling loop
expansion vessel needs repressurising
the DHW heat exchanger is leaking so cold main water passes over to the heating side