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Noisy vents in single pipe steam - I'm stumped

Greg G
Greg G Member Posts: 1
About two years ago we had a new boiler installed in single pipe steam system. We are just beginning our 3rd heating season with the new system. We replaced a Weil-McClain rated at 450SF steam; 144BTU/Hr; Steam 108 MBH with a new Burnham IN-6 (450 SF steam; 144 MBH). It feeds 9 radiators for a total of about 385 SF EDR. The mains in the basement are not insulated and I have a hobby shop in the basement so I’d like to keep it warm and therefore have no plans to insulate them.

The problem we are having didn’t seem to occur in the first heating season but began last year. …. Ridiculous hissing from the radiator vents. The problem seems worse when the boiler system shuts down and air needs to return, but occurs as steam moves out as well. Last year I tried the following: boiler cleaning and skimming (and there is no surging so that doesn’t seem to be the problem … although as we begin the season this year the water is dirtier than I like so I’ve been daily draining and replacing a little water that has the darkest rust sediment … figuring that should slow down soon), then I tried boiling vents in vinegar including the main vent (Gorton #2), then replaced a few of the vents that seemed the worst culprits. It didn’t help much.

This year I figured the main vent must be the culprit so I bought a new Gorton #2 but it hasn’t really helped at all. I’m stumped, particularly given that all was quiet the first heating season. I can’t figure out what changed!

From reading various postings here I wonder if it is the location of the main vent. Unfortunately I have no extra height available. When there is noise in the radiator vents I hear little to nothing from the main vent. I thought perhaps the pipe was somehow blockednear it, but when I removed the vent I got a ton of steam coming out, so I guess that’s not the problem. Also, I find it odd that this wasn’t a problem the first season … so what changed? It seems odd that it could be the main vent since nothing changed with it, but I don’t know what else.

A few other things to note. Several years ago (with the old boiler) after poking around on this web site and reading one of Dan’s books I decided more venting wouldn’t be a bad idea, so I removed a cap that had been installed at a T where a radiator had been removed long ago which was located toward the end of the main and put another vent there. It seemed to help. It is a Gorton #1 and is in one of the attached photos.

BTW the pressure is set pretty low: 1 psi with the diff. at .75.

I’ve attached some photos of the near boiler piping including the main vent.

Any thoughts would be greatly appreciated. I’m stumped given that it worked at first and I can’t figure out what changed.

Thanks in advance for the help!

-Greg (in the Boston area)


  • ed wallace
    ed wallace Member Posts: 1,613

    the 1st thing i see wrong is the near boiler piping is not right the 2nd thing i see the main vent should be higher
  • John@Reliable_14
    John@Reliable_14 Member Posts: 171
    BTW the pressure is set pretty low: 1 psi with the diff. at .75.

    but what is the system psi. Could be a blocked pigtail not allowing pressuretrol to shut off at above settings
  • burham blues

    definitely compare your piping layout with the boiler installation instructions [prob on burnham's site]
    john is right-i suspect that the pressure has risen beyond the point where the incorrect piping can compensate.
    luckily it does not seem like an impossible job to redo some of the header, as it has not been in too long.consider a dropped header-it can use what pieces you have plus a few extra pieces, and voila-dry steam!!-nbc
  • David Nadle
    David Nadle Member Posts: 624

    I agree. First thing is check the pigtail.
  • And

    it looks like that Gorton #2 is venting two mains. This is wrong. Each main should have its own vent, and the drops from the mains should reach below the waterline before tying together. With the present setup, if steam from just one main reaches the vent and closes it, it won't be able to finish venting the other main, and the radiator vents on that main will be noisy.

    And have that boiler repiped according to the manufacturer's specs. It's wrong.

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