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Please help identify type of two-pipe steam system


I have a 80+ year two-pipe steam system that does not appear to have any traps (pictures attached).  The name on the radiators is "The H. B. SMITH CO.".

- Does the radiator not have a trap, or is it a Return-Elbow-Trap aka Vapor Orifice?

- There does not appear to be an F&T Trap on the system (plumber also did not find one).  Is that an issue, or are some systems designed this way?

- The main supply line and dry return are linked by this U shaped plumbing in the attached picture(sb vertical with water at bottom of U).  Note that the piece of insulation covers a pipe to a radiator. The main supply line makes a big linked circle around the perimeter of the basement, but does not run directly into a dry return as I see in books. What is u-link for( perhaps a way for trapped condensate to easily return to boiler)?

Thanks in advance for your help!


  • MTCMTC Member Posts: 181
    Probably can't help you with the traps question

    but that u-shaped pipe is a water seal. It functions similarly to an F&T trap with no moving parts. Think of the P-trap under your sinks, it creates a seal of water until enough condensate is present to spill over into the dry return, and air under pressure will work its way through the water seal slowly as well, but steam won't.

    With this setup, I'd want to see some good main venting on the end of the steam line, as air doesn't quickly leave the system through the water seal. It will help to balance the system and reduce run times/fuel costs.
  • jumperjumper Member Posts: 997
    are you sure it's two-pipe ?

    I think I remember one pipe buildings with radiators connected top and bottom. Instead of vents, air was evacuated in the boiler room.
  • oldsteam85oldsteam85 Member Posts: 7

    I'm fairly certain it is a two pipe system as one insulated pipe will run from the supply-main to the radiator, and the other is connected to the dry-return.  Also, all of the radiators get hot at once, rather than one after the other as they would if connected in series.

    The air does move in and out through a large vent on the dry-return near the boiler, but this is in line with "We Got Steam Heat!" book description of two-pipe systems.

    If the radiators used a return-elbow-trap/vapor-orifice discussed in the same book, would it look like the picture of the elbow?
  • JStarJStar Member Posts: 2,668

    That is two pipe steam. The elbows may be return traps. That looped piping is a water seal that acts like a steam trap.

    Do you have more pictures? Around the boiler? Any other radiator valves or weird looking devices?
    - Joe Starosielec
    [email protected]
  • oldsteam85oldsteam85 Member Posts: 7

    There is nothing else that appears unusual about the piping, and the layout around the boiler is in line with the "We Got Steam Heat!" book.  The boiler is 5yrs old.

    Please see a picture of the main vent which sits on top of the return line, above the boiler.
  • SteamheadSteamhead Member Posts: 11,380
    edited February 2013
    It's an Orifice or "Tudor" system

    those return elbows are probably wide open. There are orifices built into the original radiator shutoffs so the steam won't reach the returns if the pressure is kept low. It looks like the shutoff on the rad in the pic has been replaced at some point, and may need re-orificing.

    The loop seal acted as a safety valve- excessive boiler pressure would blow out the water, and the steam would escape thru an open pipe which vented the dry return.

    Frederic Tudor patented the Orifice system in 1885. That's why they aren't too common here- he wanted his patent royalties. But he never gained control over the patent in Europe, so his system became popular there: 

    Are there any vents on the steam mains, or just the one pictured on the dry return?
    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.
  • oldsteam85oldsteam85 Member Posts: 7

    There is only the one vent for the whole system on the return above the boiler. 

    The valves on the first two floors are all the same as the one in the original picture, and all off the radiators in the attic are the same as the one in the attached.  It's possible that they replaced all of the first two floor valves at somepoint, although the attic ones may be original as they have wooden knobs.   There does not appear to be an orifice on these valves.

    Thanks to all for your help.
  • Dave in QCADave in QCA Member Posts: 1,660
    does it make any sounds?

    On the new valves, or the original valves for that matter, when the boiler is running, do you hear any sound of steam going through the valve?  It would not be exactly like a hiss, but a soft sound like  you can hear steam whirring throug the pipe?  If so, there are probably orifices in there.  Perhaps when some of the valves were replaced, if the guy knew what he was doing, he would have put orifices in the valve unions.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • SteamheadSteamhead Member Posts: 11,380
    What manufacturer's name

    appears on the wooden-handled valve? I can see something there but the camera's flash obscures it. And are there any markings on the top of the valve, or the back?
    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.
  • oldsteam85oldsteam85 Member Posts: 7
    valve name

    The name on the original valve is ADSCO.  Interestingly, when you look down from above a plate will say, "open, 3/4. 1/2, 1/4, shut" which corresponds to how open the valve.

    Only one of the old attic radiators regularly gets very hot, and I'll need to report back on whether it makes noise.  Some of the replaced valves will make a hiss, but it seems more like steam leaking around the stem, like a faucet does when it needs to be repacked.

    Thanks for the literature on Tudors and I'll need to read through it, but at first glance it appears that the return lines would not normally have much condensate in them, but mine generally do get heated.
  • gerry gillgerry gill Member Posts: 2,669

    is the american district steam company which means those were orifice inlet valves and you should be able to replace them with an orifice valve made today.

    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • SteamheadSteamhead Member Posts: 11,380
    The ADSCO was an Orifice system

    on which the dry return was vented into the chimney flue. This helped pull air from the system. Probably not a good idea to try that now unless we can come up with something to keep steam from getting into the chimney.

    This system appears on page 261 of "The Lost Art of Steam Heating".

    We don't know if the ADSCO people paid Mr. Tudor's patent royalties......
    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.
  • oldsteam85oldsteam85 Member Posts: 7

    Thanks for your help Steamhead.  I've bought "The Lost Art of Steam Heating", and it was very useful.

    -Is it possible to make the system run reasonably OK using the simple valves which are on the first two floors by adjusting the opening so that ~80% of the radiator gets hot?  I've played with this, and it has helped to get more heat to a troublesome 2nd floor radiator (gurgling/hammer in the pipes probably due to poor pipe pitch below floor) and the 3rd floor ADSCO valve radiators.  Before the adjustment, you could feel heat trying to reach a 3rd floor radiator from a return.

    - You have to crank up the heat for several hours in order to get any heat to 2 of the four third floor radiators.  1 of them does not get hot at all, but 1 works fine.  I suspect that the orifices may be clogged.  Is it possible to have someone clean the orifices, or do they generally need to be replaced?  Given that a previous owner must have replaced all of the first and second floor ADSCO valves with simple valves for a reason (may not have understood system either), is it common for orifices to clog up?

    Any recommendations appreciated

  • Jamie HallJamie Hall Member Posts: 6,705
    You have a lovely system...

    and it is amazing what one can do with it!

    The very first thing to do is to make sure that the operating pressure  is low enough.  Eight ounces cutout is going to be ample.  Until you get that adjusted, fiddling with valves and orifices isn't going to help much.

    Once the pressures are right, then... yes, it should be possible to adjust the various valves so that the radiators get more or less evenly hot over their length at the same time.  This is going to require some patience, however.  Take your time.  Attack the ones which seem to be getting fully hot first, though, and cut them back; they will let steam into the returns, which will unbalance the system.  Given time... or if you are a glutton for punishment, you can try fitting various size orifices until it works right.  I'm lazy; I fiddle with valves (and hope that no one comes around after me and messes it up...).

    If there are radiators which still don't heat after the others are under control, it is remotely possible that either their valves aren't opening properly -- it's not unheard of for the valve disc on globe type valves to become detached -- or that there are clogged orifices.  Or that there is a sag in the pipe, trapping water and either preventing steam from getting to the radiator, or air from getting out.  This may require some sleuthing.

    Venting is, in my humble opinion, best done at the boiler, where the dry returns drop to the wet return.

    Have fun!

    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
  • Charlie from wmassCharlie from wmass Member Posts: 3,923
    Since the first floor radiator valves

    have been changed they are stealing the steam and getting steam to the vent too quickly. You should look into adding orifices to the first floor radiators and increasing the venting at the boiler. I would highly recommend an ounce scale vaporstat to keep the pressure down too.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
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