Vaillant ecoTEC - Pressure increasing over time (when cold)?

[TheFunk]

Hi, The water pressure in my central heating system is increasing over time.

Last week the pressure in the system was 2 bar when cold. I reduced it to 1.5 by draining radiators. 7 days later it has crept back up to 2. Yesterday it was 1.9.

Could the inlet valve be slightly open (it feels like it's in the correct position) or could it be something else? Both valves underneath are in the same closed position.

I had my boiler serviced last week, shortly afterwards my wife had to increase the pressure in the system as it had dropped below the minimum pressure to operate and filled it to 2 by mistake.

Thanks

 

[Agile]

Any inlet filling valve can be leaking.

Often plastic knobs are not turning the metal shaft because the soft plastic has worn!

Tony

 

[TheFunk]

Thanks, I don't have a lot of confidence in one of the plastic knobs.
so could well be the case.

Do you know if it's possible to close the valve without them, perhaps unscrew the knob and turn valve with pliers/screw driver?

 

[Agile]

Yes,

But you normally need a smaller adjustable spanner to get a good grip.

Tony