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slow leakage on CI baseboard (water heating) air pressure testing

I am installing CI baseboard in one of my rooms. There are four sections in the big room. Three of them are longer than 10 feet. I did air pressure test on all of them with air vent installed. There is a slow leakage on one of them. I can see the leakage is from the air vent with soapy water. The pressure dropped from 30 to 25psi in one hour. Doesn't matter how tight I turn the air vent, there is always a little. Is that small leakage will be ok when water is in?

The air vent comes with the CI baseboard. It is not the automatic air vent type. I changed the air vent. It seems both of them are not good enough. But they may be good enough for water?



  • icesailor
    icesailor Member Posts: 7,265
    If it leaks air, it will leak water. Put a 1/8" brass nipple and cap on it with pipe tape and dope. See if it still looses pressure.

    Put some pipe sealing compound on the tapered part of the air vent and see if the air stops leaking.

    On the sections "longer than 10 feet", are they long enough to need a leg in the middle? A 5/16" bolt that screws into the middle of a long length. I think the length is over 12 feet but I can't remember. If you need the leg, and don't use one, the middle will sag and possibly cause a leak or break the bolt flange in the back that holds it together. Hopefully, your intermediate sections are drilled and tapped for legs.
  • heatingFun
    heatingFun Member Posts: 84
    Thank you icesailor. I will try to tight it again.

    Yes, I do have bolt to support in the middle. I am using #9 CI. The support bolts are included.