boiler losing pressure

[icarusbop]

Help - i have a combi boiler which keeps de-pressurising it needed re filling every 4-5 weeks. I found a small leak on a TRD and replaced the valve.
now it needs to be re pressured every couple of hours and there is no apparent leaks.

does anyone have any ideas what can be causing this?

The system does not seem to have a bypass valve, could this be part of the problem?

thanks in advance

Ian

 

[Ant]

Have a look outside where the overflow/vent pipe is. You may find it is letting water out there. Mine did this due to a dodgy pressure vessel.