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Intermittant problem with one-pipe steam radiatior

I have a one-pipe steam system that has generally been problem free. Over the years I've occasionally had radiators that don't heat up. In every instance the problem was solved by getting a new air vent. However, I now have a radiator that sometimes heats fine, and other times is stone cold. I've changed the air vent a few times. Each time the problem clears up for a month or two, and then goes back to this intermittant problem. I've been told that I need to flush out the radiator. However, it is on the 2nd floor, and is too heavy for me to get downstairs. Is there anything I can do to clean it out upstairs? Also, what would be the best way to flush it, even if I could get it outside? And finally, is this what I need to do at all, or is there something else causing this issue? Thanks.


  • Jamie Hall
    Jamie Hall Member Posts: 16,646
    Flushing the radiator is almost never required. Sounds great, but doesn't do much. However, the first thing I would check would be the pipes going to the radiator. Has, perhaps, some horizontal line somewhere along the way sagged just enough to trap water? I would expect a water hammer in that case, but these things are funny and it might not hammer.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Packer44
    Packer44 Member Posts: 5
    There's no hammering, but I'll try to check the pipe. Would that create my situation where the radiator sometimes heats up, and sometimes doesn't? Also, when it heats, it heats well, all coils completely filled with steam. Feast or famine.
  • Ironman
    Ironman Member Posts: 6,476
    What pressure is the pressuretrol set to cut in and out? What high and low pressure do you see on the gauge?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Packer44
    Packer44 Member Posts: 5
    The cut-off is set under 2. I should say that presently the heat hasn't been turned on; this is a persistent problem from the last 3 years, and I was trying to figure it out before the winter sets in. As for the horizontal pipe leading to the radiator, I don't have any access to it. But there is another radiator in the adjacent room very close to the problem one (I assume on the same horizontal line), and it doesn't have any problems.
  • Fred
    Fred Member Posts: 8,518
    Also check to make sure that radiator has a slight pitch back towards the steam pipe. If it is pitched the wrong way of level, it will hold water, maybe enough to cause the steam to condense as it enters the radiator. As has been said, flushing/cleaning out that radiator is a waste of your time. Not necessary. And, BTW, even though the pressuretrol may be set at 2 PSI, doesn't mean it is properly calibrated to keep the pressure in that range. Put a 0 - 3 PSI Gauge on the boiler, if you don't have one so you can see what the system pressure is actually doing. What type vents are you using? The cheapies from HD are a waste of your money. Use the Vent-Rite #1 or Hoffman 1A Both allow you to adjust the vent rate.
  • Packer44
    Packer44 Member Posts: 5
    Ok, thanks. Will make sure it's pitched correctly, and will take your advice on getting the better vents. Will also verify pressure. Given this is an intermittent problem, it may take some time to see if it's truly corrected. will let people know. Thanks again for the help.
  • MilanD
    MilanD Member Posts: 1,159
    edited October 2017
    > @Packer44 said:
    > I have a one-pipe steam system that has generally been problem free. Over the years I've occasionally had radiators that don't heat up. In every instance the problem was solved by getting a new air vent. However, I now have a radiator that sometimes heats fine, and other times is stone cold. I've changed the air vent a few times. Each time the problem clears up for a month or two, and then goes back to this intermittant problem.

    That is quite odd issue. Where on your system is this radiator? Closest to the boiler? Farthest? What vent are you using? Is your op pressure truly below 2 psi? As Fred said, pressuretrols can be wildely inaccurate, and pressure may be building higher than needed. In all, with good venting it should never go above 8 oz. Do you play with the supply valve when the rad stops working?

    If new vent solves this problem for a few months (and you don't try working the valve at all), there is your problem: vent gets plugged up or blown shut on high pressure. It's quite possible your steam velocity is high coming into the radiator, or that some dirt is kicked up inside the pipes and wedges itself inside the vent. The vent can also get waterlogged. Next time the rad stops heating, turn off the system, wait for pressure to go down, remove the vent and turn on the system again until it starts steaming. If you feel the air coming out of the 1/8 vent hole, shake your vent to loosen up any water and dirt and screw it back into the rad. Then feel if you can sense the air coming out of the vent itself. You can also swap the vent from a different rad and see if the trouble follows the vent. This will rule it out. My money would be on high op pressure and stopped up vent.

    This next is a wild guess as you didn't mention this, but I've seen it happen and act exactly like you describe. If you are trying the valve when the rad stops working, and I'm assuming you are as I would if it were me, it's possible the closing disk has detached from the stem or is otherwise loose on it inside the valve body and sometimes gets itself in such and angle to stop steam. Then you jiggle it, it opens enough to work for a while and then falls down again. Wild guess here.

    Back to the vent - also make sure your main vent is working. If not, it may be a good time to get the Big Mouth vent for the main too. Best one out there.
  • New England SteamWorks
    New England SteamWorks Member Posts: 1,428
    Sounds like a venting issue to me. Send us some pics of your main venting please.
    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
  • Packer44
    Packer44 Member Posts: 5
    As it turns out, I'm having a new boiler installed on Tuesday. (Old one is 28 years old and just started leaking). Once done, I'll check on the pressure. The vexing thing is that this is the only radiator where this problem exists, and the problem recurs soon after a new vent is installed. The radiator is neither the farthest nor closest to the boiler (it's on the 2nd floor; I have a 3rd floor radiator that works fine, as do the others on the 2nd floor.) The suggestion that there is something loose in the inlet valve causing this intermittent problem is something to explore. ... I will admit my extreme ignorance here: I have very little access to most of the steam piping, and cannot find the main vent. [the basement is finished.]. Still, to my mind, if that was a problem it seems I would have a problem in more than just one radiator. I do appreciate all this help.
    JUGHNE Member Posts: 8,721
    MilanD had a good suggestion. That rad valve may have the disc that has fallen off and floats around in the valve.

    You don't really need the valve to shut off that rad. Turning the air vent upside down will stop most of the heating.
    The rad valves must be completely open or completely shut.
    With age they seldom shut off tightly and allow steam in but condensate will not drain out.

    If you have someone changing the boiler, you could inquire about them checking that valve. If the disc is loose it could just be removed. As long as the stem will not unscrew out of the bonnet that may be all that is necessary.

    The installers should be able to add a main vent somewhere near the boiler on the dry return.
    Please post pictures before and after the install......some people wish they would of had their new install looked at by the Wallies......before the final payment.

    The new boiler comes with a book showing installation piping near the boiler. All steam piping should be black threaded pipe. BTW
  • Fred
    Fred Member Posts: 8,518
    Just because the radiator is in the middle of the house doesn't mean that it's not the last radiator connected to a particular steam Main. You really have to look at where it is connected, in the basement and if, by chance someone connected it to share a riser with another radiator in a nearby room. If so, that radiator may be stealing all the steam. If that's the case, you can try to slow the other radiator down, using a variable vent like the Vent-Rite or Hoffman 1A. and setting it to slow the venting.It may also be that on milder days, when the boiler runs for shorter cycles, steam just doesn't get to that radiator before the temp in the room with the thermostat is satisfied, especially if the rad in question is the last one connected to the main.