Five years ago I started to get a gurgling in the second floor pipes when the heat went on. I tried bleeding the pipes but in a few days the gurgling came back. Someone said I might have a leak so I shut off all the water except the boiler fill and after 8 hours the water meter did not move.

But out of desperation I added a leak stop liquid to the boiler and it cured the problem for 5 years. Now the problem is back.

My question is: if there is a contant 15 psi of water pressure created by the fill valve how does air get into the pipes? And how can I find such a small leak?

Bobv:

Some of that air is in the water, H 2 O. Heating and cooling of the water can release some oxegen that is normally in solution. Do you have stand up radiators ro baseboard ? The bleed instructions will vary. By the way, the valve does not creat the pressure, it holds it.

Some of that air is in the water, H 2 O. Heating and cooling of the water can release some oxegen that is normally in solution. Do you have stand up radiators ro baseboard ? The bleed instructions will vary. By the way, the valve does not creat the pressure, it holds it.

But I did bleed the base boards and the noise went away for a couple of days but then came back. My system is two zone with the boiler in the basement and I don't have bleeders on the baseboards.

What does the pressure on the boiler read? Hot water or steam? I'm guessing by your post it is not steam but you never know if you don't ask.