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We have a customer with a steam boiler we put in 2 months ago. He called to say that the water level is dropping out of the glass and there is a bit of hammer.

from what I see the near boiler piping is correct. The single main off the header bull heads and splits to 2 mains. Wrong way to go, but that was existing. From there nearly all of both mains is pitching up hill to the main vents. Then ends of the mains have 90° reducing elbows going to the side. Not the right way to go, but with the mains pitched as they are nothing can pool there anyway.

I ran the system for a bit, saw the water level drop, followed the steam through the system, then noticed that one of the mains gets hot on the bottom first. All I can figure from that is the water is backing up out of the boiler all the way to the main and spilling back through. The returns are all dry until they get to the boiler where they drop to the loop.

The hammer ( not very heavy) is happening about 5 minutes into the cycle, and out in the mid mains or radiator supply piping.

All the hangers on the original piping are in their original spots, so the pitch wasn't changed during installation.

What to do? I think the condensate rushing back, counter-flow style is what is causing the hammer. Does it effect the water level too? Is it causing the back up in the dry return? The loop appears to be piped correctly. Pressure barely moved off the pin. Not a lot of bounce to the water line. The water is tan/brown so maybe it needs a flush, but doesn't seem like it needs to be skimmed due to the rather stable, though dropping, water line.


  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    oh yeah

    And no insulation. he said there never was, but I'm sure there was asbestos at some point. Recommended it.
  • Danny Scully
    Danny Scully Member Posts: 1,425

    Actually Paul, those reducing 90s will gather water, no matter what the pitch. If you have a reducing fitting on the horizontal that is not eccentric, it will gather water. I am not saying this is the problem, but don't dismiss it. If this was a counter-flow system, I might dismiss it, but this does not appear to be a counter-flow system.
  • David Sutton_6
    David Sutton_6 Member Posts: 1,079
    Hey Paul

    Paul, are there any rads with the valves shut or parshly shut?  will the water level return when it cools down ??
  • Steamhead
    Steamhead Member Posts: 16,840
    edited November 2011
    Skim it

    we had that happen once with a G-8. I think there was enough oil on the water surface that when the steam finally broke free it was moving so fast it pulled the water along.

    But- are those steam mains counterflow? Where does the pipe go after the reducing 90? If it's a return line, you'll have to rework it so there is no water pocket there.

    And those Dole #4 vents look original to the system. Upgrade them after the banging is fixed.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    Thanks guys

    The reducing fitting can't collect water if the run to them is all up hill.

    The returns, after the reducing elbows, run back to the boiler, 1" pipe, and drop to the floor. There they join and go into the Hartford loop.

    Skimming sounds right Frank. It's just that there was so little bounce in the water line I was questioning it.

    The water level starts coming back while the unit is still running.

    With both mains pitching up away from the boiler, there has to be a lot of condensate coming back to the header. I think we need to cut in a drip or two. Can I do it in the one pipe going to the header, or do I need to put one on each main? These are 2" mains, one has 3 radiators and one has 5.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    edited November 2011
    Thinking about this more

    The returns are useless. They can't bring water back due to the pitch in the mains and the reducing elbows. Why would the dead men build a system like this?

    I think I need to repipe it like a counter-flow with double mains.

    Problem is, the pitch is not as steep as it should be for counter-flow.
  • I had one like that once

    It appeared the previous boiler installer did not know counterflow systems existed, so they tried to raise the main near the boiler and add return lines at the end.  Or, after installing a grossly oversized boiler into the system they tried to eliminate the banging by resloping the mains.  We went through and eliminated the "return lines" and resloped the pipe back to the boiler when the boiler failed.  Money was really tight, so we simply used oversized risers that kept the steam veleocity real low and allowed the condensate to return to the boiler.  The system heated nice and quiet after the work.  Not pretty, but helped get the heat on quickly and cheaply.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    I guess we could run the mains off the header at a 45. That would help the condensate get back without effecting the steam too much.

    The again, it's our install and we only want to do this repair one time. I didn't look to see if there is enough slope in the radiator supplies to increase the pitch of the mains, but that would be the way to go. Then separate the mains and add drips, eliminate the returns.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    Skimmed off 15 gallons and the water line was perfect. The piping is still screwy, and it still needs to be insulated, but it is working properly now.

    Thanks All!
This discussion has been closed.