Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

How to bleed air from this system? Maybe automatic?

TKH Member Posts: 3
20 year old system, new to me last year. As near as I can tell there's no air purge valve. There are 2 air vents one on top of the air scoop and one on the return pipe from the primary zone, would these be sufficient to vent? I replaced the temp/pressure valve on the tank so introduced a lot of air into the system. It auto fills. Everything ran fine for a couple of hours after firing it back up but the circ pump was bad when I got up the next morning. It is older so could just be a coincidence. About to put a new pump in and want to be sure air in the system isn't still a problem. I'd like to have a air purge valve installed but not right now unless it's really necessary. Obviously it's been filled before at least twice since the tank was replaced in 2019


  • hot_rod
    hot_rod Member Posts: 20,790
    I don’t see a pressure gauge anywhere. 12psi pressure and that air purger should do the trick

    Is the cap loose on top of the silver air vent.
    Occasionally those small float vents get plugged, it could be disassembled or replaced if you never hear air coming out
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Big Ed_4
    Big Ed_4 Member Posts: 2,534
    If all the radiation is floor level you should be ok . I would have added a purge valve set up above the gauge on the return . If radiation is higher or just incase ...
    I have enough experience to know , that I dont know it all
  • TKH
    TKH Member Posts: 3
    Thank you for the responses. The cap is loose on both air vents, I heard air coming out of the top one a little bit ago. Got the new pump installed. A neighbor suggested opening the system temp/pressure gauge to bleed air - that seemed to work pretty well.

    One more question:
    I put a pressure gauge on the tank drain valve - it's running about 22psi when heated up, that's high I think. The green valve on the input line says it should be at 12 psi, the expansion tank is an Amtrol boiler system tank that says it's pre-charged to 12 psi - rather than a valve on the bottom it has an indicator cap that should turn black if the tank has failed - it looks to be fine. I'm not sure what to look at to reduce the pressure in the system?
  • neilc
    neilc Member Posts: 2,520
    don't touch that air,
    the 12 is for a cold fill,
    now that it's hot, and the water expanded, the water is pushing on the bladder and air cushion, raising it up to what you see now,
    don't touch that air,

    what's you water pressure while the air is at 22 ?
    known to beat dead horses
  • TKH
    TKH Member Posts: 3
    I think I miscommunicated. The system water pressure is at 22psi as measured at the drain valve on the boiler. Unfortunately the gauges are temperature only. The default setting on both the expansion tank and the reducer valve are 12psi - don't know if either has been messed with.