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expansion tank full

Mcro1986 Member Posts: 8
Hey folks,
Went on a side job last night for a leaky pressure relief valve on the boiler, replaced valve but before I did i noticed the system was at 30psi (the PRV is 30psi 550,000 BTU water reg valve is a wats 12-15psi). Checked the 30# expansion tank and it is full but still has air so I know the bladder isn't ruptured. Determined that the expansion tank is to small for the system, jumped online to look for the next size up and noticed the Extrol 30# and 60# both say the accept 2.5 gal of water. Question is will I be fine with the 60#?

Could I twin two 30#?
The one that is there currently is hung on the wall down by the floor then piped up to the spiro.

the system has three zones of copper fin baseboard on the first floor and one hydro-air coil on the second floor (manual says it's 100,000btu coil)


  • SWEI
    SWEI Member Posts: 7,356
    edited January 2016
    Did you isolate and drain the tank before you checked pressure?

    Tanks can certainly be twinned, but from the layout I believe you described it may be simpler to put the taller #60 in there. We tend to use the -V models (no brackets needed) in 60 and up sizes.
    JUGHNE Member Posts: 11,074
    WAG, that doesn't sound like that large of a system to need more tank. It must have been working for a few years??
    Could the fill valve be boosting up the pressure? I like to remove the tank to check pressure, then you know it is empty of water and check air pressure.
  • Mcro1986
    Mcro1986 Member Posts: 8
    edited January 2016
    I did, was at 12psi empty, when full the tank is solid all the way to the bottom. system was installed in 2009, homeowner bought the place 3 years ago and said the home inspector even commented on the tank being full.
  • hot_rod
    hot_rod Member Posts: 22,251
    Amtrol has a sizer tool on their website. If you twin 2 check the pre charge on both
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • RJ_4
    RJ_4 Member Posts: 484
    It could be that the fill valve is rusted ,corroded internally, causing the valve to feed continuously, B&G and most Watts valves have a internal strainer which can be removed and cleaned or replaced, or in some cases the entire valve may need replacing. I would also check bypass valve if there is one. these are simple inexpensive checks that could be done before resizing tank

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