Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

New Boiler - Hammering and Leaky Air Vents

MoachMoach Member Posts: 1
I finally bit the bullet and converted my steam system from oil to gas about 6 weeks ago. The first few times that the heat came up everything was fine. Then I started to get very loud hammering all throughout the house. The hammering is primarily at the beginning of the cycle. A few days after the hammering started, water started to leak from the air vent on a radiator in the basement. That was followed by the same thing happening on a radiator on the first floor. That was the status for a couple of weeks and now another radiator on the first floor is leaking water from the air vent (so far no leaks on the second floor). I swapped a new vent on one of the radiators (a Durst A884 that I got at Lowes) and it leaked right away, so I don’t think there was a clog in the old vent. I did not have any leaks or hammering with my old oil boiler.

My boiler is a Williamson GSA-200-N-I. The PSI is set to .5. In case it means anything, the water feeder counter was ticking up once for roughly every 3 cycles for the first few weeks. Now, it’s only every 5 cycles or so.

I’m including pictures of the boiler and the leaking vents. Any thoughts on why this is happening and what I can do? The plumber who installed the boiler is blaming the pitch of my pipes and my air vents. He says the new system makes the water hotter than the old one. Did he do something wrong? I didn't expect that getting a new boiler would mean I would need major plumbing work throughout the house.


  • Jamie HallJamie Hall Member Posts: 6,706
    Is this a new boiler, I take it?

    Got to admit I'm not really keen about the riser and header arrangement...

    Clanging at the beginning of the cycle is usually from condensate or carry over getting into a line and being pushed along.  It looks to me as though it might be possible for there to be a good deal of carry over from the boiler getting into the lines -- could be one of the problems; perhaps the only one.

    Is the new boiler more or less at the same water level as the old one?  That can cause problems, too, although I don't see any once wet now dry returns in your arrangement; looks pretty simple.

    The new boiler (or new fuel) does not make the water any hotter.  It may make steam faster, but not hotter.  Steam is steam...

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

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • SilSil Member Posts: 72
    edited December 2012
    Install Manual

    I am a homeowner that is getting an oil to gas conversion soon - and no steam expert... but according to the installation manual of your boiler the riser and header are supposed to be 3" pipe.  The header on your install does not look 3" to me.

    Also I am not sure if you have the full 24" from the waterline to the header either...

    (see page 11 in the pdf of the attached link)
  • BobCBobC Member Posts: 4,453
    Poorly piped and dirty

    that steam header is supposed to be at least 28 inches above the water line of the boiler, it looks like the installer lust decided to use whatever was there before - just because it was piped like that before does not mean it was right. New steam boilers are very fussy about the near boiler piping and this just is not done right. the reduction from 3 to 2 and than back to 3' is also not helping matters. The picture below is out of the install manual and has to be adhered to.

    Has the boiler been skimmed yet? New boilers introduce oil and other debris into the system and all of that has to be removed by skimming to get the boiler water clean. Dirty water causes all sorts of problems (water hammer and vent spitting) and has to be corrected. After the boiler is skimmed, install new radiator vents and also install a main vent that is sized according to the amount of air in the boiler header and steam main.

    Call the installer back and tell him the boiler has to be piped per the installation manual and it has to be skimmed. Don't pay him till it's done right! Then have him replace the vents and check that the main vent is large enough. You will probably have to pay for the vents unless they are included in the contract you signed or you could buy and install them yourself.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • RJRJ Member Posts: 484

    I agree with all    also looks like header pipe size is reduced
  • JohnNYJohnNY Member Posts: 1,823
    My goodness...

    ...that's a mess. Please tell me you didn't pay for that installation yet.

    It needs to be done by someone who installs steam boilers.
    For private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    Or at Gateway Plumbing & Heating
    John travels regularly to out-of-state clients for consulting work.
  • TomMTomM Posts: 233

    the manufacturer recommends a 20" or 24" vertical pipe out of the boiler to only allow steam into the system, preventing water from going up the pipes.  Since the pipe out of the boiler is short, you have a ton of wet steam (ie water) going out to your system and that's most likely why you're having all the problems.


    #1 Fix the near boiler piping.  Yes, it must feel like tragedy, but first things first.
    beautiful Conshohocken PA
  • Hap_HazzardHap_Hazzard Member Posts: 1,349
    Check out the relief valve.

    This install doesn't meet code, let alone the manufacturer's specifications. They need to repipe this thing.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!