Constant falling pressure guage on combi boiler?

i think you will find the most common cause is the expansion vessel has failed, it can either be replaced by your boiler manufacturer although can be costly or have a alternative expansion vessel fitted somewhere else in the house as i did in the cloakroom, we had been recharging every morning, the expansion vessel has a balloon type affair inside which fails to maintain the pressure if damaged and results in the boiler failing, anyway any decent local plumber should be able to help, the parts are cheap if sourced like i did from plumb-base and paid the plumber £75 to cut into the radiator circuit and stick in the vessel, pressure test etc, all has worked well now for over 8 months without one recharge!!

stuart
July 2010

I had exactly the same thing in my last house. My problem was caused by having solar panels fitted which pre-heated water before it entered the boiler - supposedly to save gas when boiling the water. Older boilers cannot cope with incoming water which is heated above a certain temperature. We had to constantly re-pressurise the system to get any hot water. The result was that the system became weakened to the point that it could not hold any pressure and all water was dumped through the overflow and the old boiler had to be replaced.

Sapper
July 2010