mystery pressure drop

[paul9367]

Can anyone please help solve this mystery?

I have a ferroli combiboiler which started dropping pressure pretty rapidly.

A plumber changed the AAV which had no effect and we have ruled out the pressure relief valve and the expansion vessel is fine.

We were told it must be a leak on the system so had a specialist company with thermal imaging out as all pipes are under concrete floors. He identified two possible spots and both were dug up.

The builder claims both spots were dry and so filled them in with cement again after covering the pipes in plastic. He advised we get the other firm back to do a gas test to trace the leak exactly. Since then pressure has stopped falling.

Could there be another explanation or is it likely that the leak was on the pipe the builder exposed and he has somehow plugged it when the filled in the hole with cement?

Is there any other possible cause on the boiler?

We

 

[astarquitefrankly]

when did this start? have you stopped using your central heating recently?

 

[paul9367]

thanks for the reply.

This started whilst still using the heating. It would lose pressure as it cooled and by morning would have dropped significantly.

After stopping using the heating to test if it was the heating or the boiler I isolated the valves on the boiler and pressure would stay up. It would fall as soon as I opened up the valves to the central heating again.

However, valves are now still open to the central heating and no drop??

Heating was on yesterday morning

 

[paul9367]

pressure is dropping very slowly but still nothing like before the specialist leak finders have been back and are baffled.

Could anything on the boiler explain this???

AAV has been replaced , the prv is not leaking and expansion vessel is ok

Help!!

 

[glasgowgas]

pressure is dropping very slowly but still nothing like before the specialist leak finders have been back and are baffled.

Could anything on the boiler explain this???

AAV has been replaced , the prv is not leaking and expansion vessel is ok

Help!!

if prv is 100% not leaking and AAV is 100% not leaking you can only rule out boiler by doing this........................

top up pressure to 1.5 bar and close flow and return valves under boiler,
turn off boiler electrically.

leave for 24 hours

no pressure drop = system leaking

pressure drop = boiler leaking

 

[paul9367]

thanks for your help, will do that