Boiler pressure dropping - is a leak the only cause?

amin1992

Hey everyone, thanks for your advice here. Our home has an old 1976 oil-fired boiler that, despite being old and loud, has ran like a dream. It heats 2 loops and also has a domestic coil for our hot water.

Boiler had an autofeed Pressure Reducer Valve installed 4 years ago, which has a ball valve after it. We've always left the ball valve off and pressure has remained the same for the 4 years (~12 PSI).

I walked in the room a few days ago to notice the pressure was lower, looked to be about 7 PSI - hard to tell on the little gauge obviously as it just increments every 10 PSI. Kept an eye on it all day in case it was just fluctuating and it was still low.

I opened the valve to the pressure reducer valve and let it refeed up to around 12 PSI. Shut the ball valve.

3 days passed and I noticed it has dropped again, down to 10 PSI. I'm tempted to just leave the ball valve open and let it feed to top up, but I'm nervous of a leak now. The lower level loop is encased in the concrete slab, so if there is a leak, it's down there and it's never going to be found. I have confirmed everywhere else that there is no leak.

What do you think? Any other reason the pressure would be dropping? Should I just open the valve and let it remain open and keep an eye out for leaks?

EdTheHeaterMan

You have a leak

amin1992

I stand corrected. Found the leak! Now to figure out how to replace a joint that goes halfway into the wall... ugh

EdTheHeaterMan

Remove the wall. Repair the leak. Replace the wall. Paint