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Venting Steam Heating system

Todd_29 Member Posts: 3

Thanks for the tips!

Pipes are all insulated.

I have an adjustable vent valve on the offending radiator. If I don't leave it wide open, the banging occurs in the pipes closer to the boiler.

I don't think this system has a main vent valve at all. I have not seen it. Could that be the problem?? Is that something difficult to install?




  • Todd_29
    Todd_29 Member Posts: 3
    Venting Steam system - water knock


    I have a one pipe steam system. The radiator farthest from the boiler always bangs. The only venting on the system is through the valves on the radiators. Would adding a vent in the main pipe in the basement alleviate the knocking? I'd appreciate any thoughts. I am thinking that the venting is inadequate, thereby causing the water knock.

  • Dave_4
    Dave_4 Member Posts: 1,405
    I'd check the following:

    in this order:

    1) Make sure the boiler pressure is under 2 pounds max.

    2) Make sure all the rad-valves are wide open.

    3) Make sure the offending/banging rad has a medium to smaller sized vent orifice; unless it is a cool room.

    4) If the steam main is not insulated. Stop! Insulate it COMPLETELY!

    5) If the main air vent is older than 10-years, replace it with the largest orificed available, something like a Gorton steam main vent with a hole you can drive a Buick thru (:-o)
  • Steamhead (in transit)
    Since the banging occurs

    in the very last radiator on the main, and moves closer to the boiler if the last rad's vent is throttled, it's possible that the return line that comes off the end of the main is plugged. This would allow water to back up into the steam main, where it would cause the banging.

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  • Todd_29
    Todd_29 Member Posts: 3
    Great point

    Hi Steamhead,

    That makes a lot of sense. When I use heat the first time during the season it heats the first time quietly, but then the banging starts.

This discussion has been closed.