Boiler pressure at 27psi....

George_15

I noticed the boiler pressure on my gas fired boiler was at 27psi. the other day. I drained the boiler till the pressure dropped to about 18 but today it was at about 27psi again. I usually leave it at 15-17psi since its in the basement of a 2 story building. I have 2 Amtrol Extrol #30 expansion tanks, and I was thinking that perhaps one of them is bad. All the zones currently have heat, and it doesnt look like the pressure relief valve has gone off yet since it hasnt hit 30psi yet and I dont see any water on the floor.

Assuming that a leaky pressure reducing valve is not the issue (I will verify this by closing the valve right before the pressure reducing valve) am I correct to assume that one of the bladder expansion tanks is bad?? I tapped on both of them but didnt hear any audible difference. Can I verify which one is bad by just opening the schrader valve on each and see which one lets out water? Any other ideas or if it can be something else are appreciated!

tommyoil

Its possible

That one or both tanks have lost their factory charge (12 psi). If you open the schrader and water comes out its bad for sure. That schrader is on the air side of the bladder, not the water side. Water would indicate bladder failure. If you have pushed on those valves in the past, chances are you have reduced their ability to absorb the expansion by reducing the factory charge to zero. Dont forget, those tanks have a rubber bladder which, much like a balloon, will lose their charge over time. You can remove them,(the tanks)and check the charge with an ACCURATE tire pressure gauge. I use a digital gauge. The tank charge MUST match the system operating pressure or they will be prone to pre-mature failure. You can then either pump them up to match the system pressure with a bike tire pump, or, if they are older just replace them. If you choose to replace them, make sure they(the new ones) are charged to match the system pressue before you put them in service. Hope this helps.