loosing pressure from a Baxi

[sasik]

Baxi Combi Boiler loosing pressure all the time. I checked all the rads in the house, all the pipe work even lifted some floor boards, no leak any where!
I then looked around the boiler, no water dripping from the discharge pipe, no water dripping from any of the fitting at the boiler. I then checked the expansion vessel. The air pressure was very low so I pumped it up to the right pressure (1.5bar) then top-up the water pressure (2bar) the boiler worked fine. 3 hours later the water pressure at the boiler dropped to 0.5bar!

I run out of ideas. Where is the problem?

 

[sonray ltd]

have you rechecked the vessel pressure ?

 

[andsam]

When repressurising the expansion vessel make sure you leave the drain off open to allow the water been pumped out of the ex/vessel to leave the system. I you dont your foot pump can give you an incorrect pressure reading.

Exp/vessel pressurise to 1 bar approx. (with drain off open.)
system pressure set to 1.5 after the above.

 

[sasik]

OK, I didn't know that. But do you still think I will need to re-pressure the vessel with the drain valve open even if at the time the water pressure in the system was very low?

 

[andsam]

yes it could make a difference.

 

[plumberdan]

This is rare but ive came across it before...

There could be a crack in the heat exchanger and the water from heain will be leakin internally through heat exchanger and leaving system via the condensate.
To check if this is the problem you would have to disconnect the condensate or cut into the condensate pipe and check to see if water is leaking from it when heating is off.

just a suggestion hope it helps!

 

[sasik]

I didn't check this thread for a wail and it did came to me (before I read the last post from

plumberdan​

) few days ago the

possibility​

of an internal leak in the boiler due to a

cracked​

heat

exchanger​

and water

vaporizing​

away from the system when it's running.

So as last

resort​

I

decided​

to add to the system a bottle of "leak seal" and to see what happened! The customer keep checking the pressure in the system and the pressure is still 1.5bar after one week!

Plumberdan​

, I think you hit the nail right on the head!

Thanks

Sasi