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Loud one pipe steam heating system

Hi Guys,
I am hoping that you can help me with a one pipe steam heating system in my home that is very noisy in operation.
I have laid out the details below and the specific observation that I feel is the key clue.
Ex. The boiler is 'hot' but flame off for 5-10 minutes, water line comes back up, close to normal.
*then we call for heat, flame on, since it is 'hot', it takes just a little time to produce the following effect.
The water gage will bounce, then go lower and lower, some water returning from top of water glass, and the water will disappear below the glass.
The boiler will have some vibration/rumbling.
Loud noises, will occasionally be produced at boiler but rare.
Some banging in steam branch piping does occur but no consistency to timing/frequency/or even location.
Why would the water gage seem to go into a negative pressure (meaning it looks like the water level is pulled down into the boiler....happens within 3-5 minutes of turning the hot boiler to flame on.....
We have had radiators added and removed in the home.
We have a very old and unknown condition of the interior of the return lines (we may have them flushed)
We have cleaned the boiler twice with standard steam boiler cleaning product which did remove a significant amount of sediment. But little or no change in noise level/ banging.
We verified the pigtails; of the pressure control is not clogged and has a small amount of water in it as a trap to protect the pressure control.
The pressure control is set as follows
Cut in = 1/2 psig. Differential = 1, Cut out - cut in + differential.
Our boiler gage always shows 0 psig so we are ordering a test gage (with valve, for testing only), 0-3 psig. This will help us to see minor changes in pressure to eliminate the pressure control as a/the problem.
Boiler is standing pilot. Burners are clean. Gas pressure at manifold 3.5" wc.
Steam mains (2) have new steam vents.
Please see floor to water line/manufacturers water line measurement.
Please see floor to Hartford loop measurement
Please see photos.

Bottom line
Noisy operation/ banging pipes/severe drop in water line then restores shortly after off cycle.
Can you help with further diagnostics?
Can a clogged return line on a one pipe system pull down the water line?
We do not have any overfeeding occurring.

Thank you


  • mattmia2
    mattmia2 Member Posts: 7,156
    Did you skim the boiler after you added the new piping?
  • Jamie Hall
    Jamie Hall Member Posts: 20,432
    Was nything changed in the near boiler piping? Header? Equalizer? Connections to steam mains?

    You are not getting 'negative pressure". What is happening is that for some reason -- most likely piping errors -- the water is getting pushed out of the boiler by the steam and winding up elsewhere in the system. Once it is there, it collides with steam going the other way -- in an unpredictable way -- and makes the banging.

    Step one will be, as @mattmia2 said, a thorough skim of the boiler. That takes time. There are no magic boiler cleaning products which will help the process.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • KC_Jones
    KC_Jones Member Posts: 5,354
    mattmia2 said:

    Did you skim the boiler after you added the new piping?


    It sounds like you are surging. You mention cleaning the boiler with chemicals, but I and many other believe skimming is the only good way to get the oils out.

    Also, what does the near boiler piping look like? That can amplify these problems if it isn't correct.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,053
    edited December 2022
    Sounds like everyone else is hearing. You have to skim the oil off the surface of the boiler water. Or your near-boiler-piping is incorrect. Can you post a photo of the pipes coming from the top of the boiler?
  • ksperling
    ksperling Member Posts: 3
    Apologies for my delayed reply. Thank you all so much for your thoughts. Near boiler pictures attached. Any further thoughts are greatly appreciated.

  • jhewings
    jhewings Member Posts: 134
    Sorry your NBP is terrible. Others will comment on how this relates to your banging and disappearing water. They say steam can be very forgiving sometimes but with all your issues, I can't imagine this can be fixed without near boiler piping redo
  • mattmia2
    mattmia2 Member Posts: 7,156
    The risers and headers are way too small and the fittings aren't arranged right, that will leave the water in the boiler no place to go but in what I assume is the header from the old boiler. That has no drip on it so the water that the boiler is pushing up in to that upper pipe has no place to go but to collide with the steam and water being pushed out of the boiler.
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,053
    As others have said, the piping is really a mess and should be re-piped. All you can try is cleaning the boiler well. MAke sure all the cleaner is out of it and that it is skimmed and clean. If that doesn't help, correct the piping at the boiler.
  • dabrakeman
    dabrakeman Member Posts: 316

    Refer to pages 5 and 6 to see how the near boiler piping is supposed to be done.
  • KC_Jones
    KC_Jones Member Posts: 5,354
    As near as I can tell there isn't anything correct with that piping and you appear to have a colliding header which is something specifically called out in the manual as what not to do.

    Banging, water leaving the boiler, rumbling would all be symptoms I would blame on that piping.

    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • ksperling
    ksperling Member Posts: 3
    Really appreciate all the feedback.