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Can't keep the pressure down! :) New expansion tank in and pressure wants to stay at 22psi

The start of the issue is that I noticed a drip around the top of my waterworker expansion tank so it seemed like cheap insurance to replace the tank and got an Amtrol 30 which matched the size of the existing tank.

I first used the factory precharge of 12psi and installed it, job done. I set the boiler pressure around 15psi cold and thought I would be good to go. The next day when the boiler was at 180 the psi was around 24psi.

I turned off the boiler feed to isolate the watts auto fill, which is only a couple of years old and nothing changed, after draining a little water to get it back to 15.

I have a fairly good sized house with 8 zones so I removed the tank and changed the charge to 15psi thinking that it was the normal pressure of the system and that anything over 15 would go into the tank. Reinstalled it and thought it would be all set.

The pressure is a little better and now goes to about 21psi.

Maybe nothing to worry about but I would like to have the system at 15 or so.

My DHW is a superstor off a zone and I dont think it's leaking in the system othwerwise it would go higher.

I am trying to determine if I need a larger tank or if perhaps the tank I had should be set higher?
I apologize if this message is rambling and not sure if I made my point.
Thank you for any advice here.


  • Ironman
    Ironman Member Posts: 7,385
    What you're describing is perfectly normal. As long as the pressure doesn't get north of 25 psi with the boiler hot, you don't need a bigger tank.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.