Vailliant EcoTech 837 - Losing Pressure when heating off

[Snork]

Hi,

Just wondered if anyone had any new ideas on this issue. I'll try and detail the issue and what has been tried after reading lots of posts of similar problems, although most others have high pressure when running or are losing pressure much slower than me.

Basically the last couple of days my boiler has started displaying a low pressure f22 error. If I re-pressurise the boiler to about 1.5bar is drops back to 0.3bar over a couple of hours which from what I've read sounds fast.

There are no visible leaks and if the heating is on the pressure rises to approx 2/2.2bar and stays there.

The expansion vessel pressure seems ok and no water comes out of the valve.
There is no water coming out of the external overflow.

Is there anything else that I can do/check as DIY or is it time to call in a professional?

Thanks

 

[Agile]

Boilers don't have overflows!

You need to search for isolating the boiler from the rads.

Tony

 

[Snork]

Thanks, will have a look at isolating. For the overflow I meant the pipe connected to the pressure relief valve, sorry.

 

[Agile]

Pressure relief valve vent pipe.

 

[Snork]

Thanks for the info, I isolated the boiler overnight and it kept pressure, as soon sI opened the flow/return valves it dropped right down so must have a hidden leak somewhere.