Will CH pressure drop if no inhibitor has been added?

[blueharvester]

We recently had our CH system converted from an open vented to a sealed system and have found that the pressure drops from 1.5bar to 0.5bar when the heating is on for more than a few hours.

There is currently no inhibitor in the system, so would this cause the drop in pressure or is it more likely that there is a leak somewhere?

 

[yerino]

Has it dropped 1 bar more than once? .. If so theres a leak!

 

[petit_pablo]

Amount of inhibitor in a system wont make any dfference to the pressure.

If its losing pressure quickly its probably got a leak somewhere.

 

[blueharvester]

Has it dropped 1 bar more than once? .. If so theres a leak!

It drops 1bar every time I have the heating on for more than a few hours. I then have to top it back up to 1.5bar.

Incidentally, I have noticed on two of the radiators downstairs, when cold, there is a small amount of moisture weeping from the valve joints. It's not enough moisture to drip but I can detect it by using some tissue paper. Would this be enough of a leak to constitute a 1bar drop in a few hours?