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expansion tanks

dana_3 Member Posts: 57
new style expansion tanks ( # 30, #60's). what is the formula to find the correct pressure on the tank, on a boiler system that is operating normally.. thanks again ..dana


  • Big Ed
    Big Ed Member Posts: 1,117
    Tank Pressure

    No formula , we use a tire pressure gauge to find out the tanks pressure.. Set the standing alone tank to match the systems needed pressure...
  • john_35
    john_35 Member Posts: 29
    tank pressure

    You have to remove the tank from the system to check the pressure. It should match the automatic feed pressure setting (usually factory set @ 12#). I wouldn't recommend you attempt this yourself. If the tank has lost it's air completely it will be full of water. I can't tell you how many times I've dropped it right on the foor! If you try to check it while it's on the system you'll only show water pressure. Check it with a tire gauge.
  • scrook_2
    scrook_2 Member Posts: 610
    set the tank...

    before installation, to the same pressure as the cold fill pressure of the system. use a good/accurate gauge on the system and a low pressure tractor tire gauge (say 2-20 psi) on the tank.
  • hr
    hr Member Posts: 6,106
    A nice gauge

    for setting expansion tanks is one from a motorcycle or ATV supply shop. They have low pressure, easy to read gauges in various ranges. This is a 15 PSI version, reads kPa also. Much easier than a pencil type gauge.

    Rough life in a tool box, however :)

    hot rod

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  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    I've taken to

    installing a threaded tee on the water side of the tank and installing a boiler drain right there so I can drain off the pressure and check the pressure correctly. Of course you need a shut off valve between the tank and the rest of the system. WW

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  • joe_31
    joe_31 Member Posts: 24
    expansion tanks

    if it has lost its charge i agree it is history. the rubber is permiable and allows air out of its bladder but should not let water in. i check them while on the system with pressure off of the boiler. i close the feeder blow off pressure at the relief into a bucket and use an electronic tire gauge from sears that is right on. :) joe
  • tim smith_2
    tim smith_2 Member Posts: 184
    setting expansion tank

    Measure the height from the base of the boiler to the top of the system. Say it's 30 feet. At appx 2 ft per lb would = 15 psi. Add 3 lbs or so for safety. Set your fill and tank pressure at 19 psi then. This will be a good # to maintain fill pressure and tank pressure. Make sure you are sizing your expansion tank correctly. PS. Ditto on removing tank to check pressure of it.
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