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Top radiator on riser heating up, but not the two below

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Rmasci
Rmasci Member Posts: 17
Okay, so I have a Warren Webster steam system in a circa 1930s apartment building I am now running.

On one riser I have 3 radiators, one in the basement, one on the first floor, capped off pipes on the 2rd, and then one on the 3rd floor.

The pipes leading to the valve get hot but not enough steam is being delivered to heat the radiators in the basement and the 1st floor. Even removing the valve only a little bit of steam is getting through the pipe on the basement, more on the 1st than in the basement. but apparently not enough to heat either. The third floor radiator, however, gets glowing hot no problem.

Possibly localized obstructions in steam pipes to each of the radiators? Steam passing through the steam trap of the 3rd floor?

The radiators on either side of it, off of the same steam main get hot just fine.


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  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    Do the two problem radiators share a return line with the radiator which gets nice and hot? If so, odds are that the radiator which gets nice and hot has a failed open trap -- especially if you notice that that return is also hot. Otherwise they could both have failed closed traps (unlikely) or the air can't get out of the return or returns which they have (also, judging from some of the other shenanigans your system seems to have gone through, quite possible).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Rmasci
    Rmasci Member Posts: 17
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    They do share a return line.

    Both the traps on the failed radiators are new and their valves both work. Upstairs however it is the original valve and 1917 patented Warren Webster trap, so a failed trap seems likely as I already encountered one of those.

    I would have changed it today but the tenant in that unit is incredibly weird about people being in their apartment. Tomorrow I should be able to do it and see how it goes and report back.

    Why exactly would a stuck open trap stop the two below it from working?

    And thank you for all the help.

  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    What happens with a stuck open trap is that it pressurizes the return -- unhelpfully, often not all of it! -- so that the air can't get out of the other radiators.

    I'd suggest just closing down the Warren-Webster inlet valve to the point where all but the last section of the radiator gets hot -- that would work too, if your pressures are low enough -- but with a slightly weird tenant you can't count on them leaving it alone. They'd open up the valve again. Try the trap.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JUGHNE
    JUGHNE Member Posts: 11,075
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    As that open trap passes steam into the return, that steam can go to working traps and close them. Those rads with closed traps cannot vent the air and therefor not heat.
    Have you felt the traps on the cold rads? Are they steam hot?
  • Rmasci
    Rmasci Member Posts: 17
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    JUGHNE said:

    As that open trap passes steam into the return, that steam can go to working traps and close them. Those rads with closed traps cannot vent the air and therefor not heat.
    Have you felt the traps on the cold rads? Are they steam hot?</blockquot

    They weren't yesterday in the past when the boiler had been running for longer I did notice in the basement that the traps were glowing hot.

  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    I think I like @JUGHNE 's explanation better -- but either way, a bad trap will do the deed...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Rmasci
    Rmasci Member Posts: 17
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    I replaced the steam trap on the 3rd floor but it still did not solve the problem, at least not in the basement. I did not get a chance to check the 1st floor.

    The radiator pipes are running across the floor and even with the valve off it will not shoot as much steam as it should.

    Could it be as simple as the steam pipe being obstructed with gunk?
  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    That pipe is a return? Does it get hot? Does it have enough pitch?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JUGHNE
    JUGHNE Member Posts: 11,075
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    Do you know if it ever worked....could be too long/small of a pipe.
  • Rmasci
    Rmasci Member Posts: 17
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    JUGHNE said:

    Do you know if it ever worked....could be too long/small of a pipe.

    Not sure if it ever did. Has not worked this season as far as I have seen.

    That pipe is a return? Does it get hot? Does it have enough pitch?

    One is the steam and one is the return. Pitch does not seem to be the issue as even with the steam valve completely detached from the tadiator only a little bit of steam will come out. The pipe itself usually gets hot but the radiator will not.
  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    If only a little steam comes out of the steam pipe even with everything detached (brave man)... something else is going on, and it seems odd that it would be the doing the same thing on the lower two floors and not the upper one. Like... very odd. I assume that it is quite certain that the same riser feeds all three floors?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ethicalpaul
    ethicalpaul Member Posts: 5,731
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    Maybe water collecting in a sag killing steam in the radiator runout coming off the riser? Can you see it, or is it hidden in the floor?
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • Rmasci
    Rmasci Member Posts: 17
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    If only a little steam comes out of the steam pipe even with everything detached (brave man)... something else is going on, and it seems odd that it would be the doing the same thing on the lower two floors and not the upper one. Like... very odd. I assume that it is quite certain that the same riser feeds all three floors?

    Yes, it's certainly the same riser.

    The unit above I am going to change the tap and valve to see if that might remedy her problem.

    I am feeling that the basements problem has to do with some sort of obstruction in the steam pipe itself that is preventing the steam from reaching the radiator.

    It has an unusually long run off of the riser with 3 bends before the valve, so perhaps upsizing the piple from 1/2 to 3/4 inch will reduce steam friction allow it to pass.
  • Rmasci
    Rmasci Member Posts: 17
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    Maybe water collecting in a sag killing steam in the radiator runout coming off the riser? Can you see it, or is it hidden in the floor?

    It appears to have a good slope to it but I am going to repipe it anyway.
  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    half inch is too small a feed pipe for any radiator -- inch would be better. What size is the radiator?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    edited February 2020
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    Unscrew the bonnet of the valve, and check the disk of the valve not to have come off, and put a level on those pipes, to verify good slope.
    It is very unlikely that the pipe is plugged-this is not like a drain pipe from a sink, or a wet return.—NBC