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Steam Boiler Noise

ManusManus Member Posts: 2
I have a relatively new oil fired boiler (~10 yrs old) in a 1939 two pipe steam system.  It's been a quiet, reliable system...that is until this winter.  I had some work done this past summer in an upstairs bath and guest room, that required unhooking two radiators to re-do the floors.  The bath radiator was reinstalled, but the guest radiator was replaced with a slightly smaller width unit, that required the supply side to be re-piped.

Now the issue -- for the first time since I bought the place 6 years ago, I'm getting loud clanging/banging in the piping on occassion, when the boiler is firing.  It doesn't happen every time -- it can be quiet for days.

Is it possible the plumber piped the guest room unit improperly, so that there is condensate pooling at a low point in the steam feed line?  It's now buried in the ceiling, so there's no easy way to check.  What to do?

Also, I checked the site glass on the boiler and the water level is pretty high up in the glass -- essentially at the top of the glass.  It has an auto fill system.  I thought that might be contributing to or causing the noise problem, so I thought I would drain a few gallons out of the condensate return, to drop the boiler water level to the middle of the site glass, but when I opened the drain valve at the condensate return, instead of water coming out, it was sucking air into the system.  Is there a different valve I need to open to drain a bit of the water out?  Any other ideas or solutions on the water level and the noise?

Thank you.


  • SteamheadSteamhead Member Posts: 13,866

    you may have some old vacuum vents on that system. These should be replaced since they can hold water up in the pipes. Then the boiler feeder will come on to maintain the boiler's water level, and when the water finally returns from the system the boiler will overfill.

    Where are you located?
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Jamie HallJamie Hall Member Posts: 12,947
    Couple of thoughts...

    first, in something like this my first reaction is: it worked before (i.e. was quiet) and it doesn't now (i.e. it bangs): what changed?  That's always the first place I look when something goes wonky on me.  And it is possible that the new plumbing is holding water somewhere and banging.  Only thing about that is... it's rare indeed for a water hammer to happen only once in a while.

    The high water level could definetly be a problem.  The possibility I might ask there -- in addition to Steamhead's comment -- is that of the auto feeder leaking or, if there is a manual bypass, the manual bypass leaking.  Valves do, after a while.  Is there another shutoff valve on the water supply you could shut off for a bit, to see what happens to the water level in the boiler?  Once you get it down to some reasonable level?  Only do keep an eye on it if you shut off the auto feeder!  Another possibility is if you have a tankless hot water coil on the sytem -- could that be leaking just a bit?  They do, sometimes.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ManusManus Member Posts: 2
    Thank you!

    Thanks, Steamhead.  I'll check the vents.  I'm actually reading "The Lost Art of Steam Heating" (got it for Xmas), so between that great reference, help from folks on this site, and doing a little searching on the web, I should be able (hopefully) to figure out if I have vacuum vents.  I also understand from "The Lost Art" that corrosion in the condensate return lines can slow the water return, causing the auto fill to top off the boiler.  Guess that requires a system chemical clean?  To answer your question, I'm located in Boston.  Got a good steam recommendation for this area?

    And thank you too, Jamie.  The intermittent nature of the problem is a bit of a head scratcher.  My thought is that the system is just marginally overfilled and/or the new piping is just a tiny bit out of sorts.  Not sure.  Maybe jacking up the radiator an inch will help?  The steam and condensate lines have a long (10 ft?) horizontal run between a pair of floor joists, so I should be able to do it without unduly stressing anything.  As for the boiler, I do have additional valving on the water feed to the boiler upstream of the autofill and the bypass valving, so I can close the water supply down and monitor the water level.  Given that it's a two pipe system, it shouldn't be using a lot of water.  And there is no tankless hot water coil -- I have a separate gas-fired HW tank system.  I would just like to be able to drain the boiler down a bit to get into the middle of the site glass to see if that fixes the problem.  I can then move on to the rising water level issue.
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