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Inlet valve banging when closed, hissing when open

On the top/4th floor of a 100 year old apartment building in NYC with a one-pipe system.

One of my steam radiators does something a bit funny.

When the inlet valve is closed, I'll hear a banging when the heat comes on, sounding like it's coming from the pipe/inlet valve area itself. I'd thought that this steam/water banging noise could only happen when the valve is open. And yes, I'm definitely closing the valve fully and tightly.

On the flipside, when the valve is open, occasionally there's a hissing noise that sounds like it's coming from the inlet valve itself - you can see a video of it here: <a href=""></a>

Also, when I close the valve on a hot system (because the hissing is driving me nuts) just a few drops of water drip out of the pipe that feeds into the radiator itself.

The super is mostly uninterested, any ideas on what I can do?



  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,485
    Disinterested super

    Try leaving the inlet valve fully open, and rotate the air vent so it points down.

    It sounds as though the pressure may be high enough to force steam through the closed valve, and when the condensate builds up, causes water-hammer.

    Se if you can go above the super with your complaints-maybe to the person who signs his check, and would like to know that deferred maintenance is costing him money.--NBC
  • brooklynquestion
    brooklynquestion Member Posts: 6

    smart idea - i just flipped the air vent & opened the valve - will report back.
  • brooklynquestion
    brooklynquestion Member Posts: 6
    edited April 2014
    same result...

    sadly still getting the same banging even with the flipped air vent and open inlet valve.

    also, this radiator is warming up - though not at full scorching heat, at least not yet - despite the flipped air vent...

    it's also continued hissing at the inlet valve.

    any ideas on what's going on?
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,485
    Radiator vent

    Post a picture of that vent, so we can determine the make. Those vents with floats will shut off when upside down, but some cheapies may not. --NBC
  • ChrisJ
    ChrisJ Member Posts: 11,612

    Agreed pictures will help.

    Hissing inlet valve sounds like the packing nut is leaking. This will let air out and steam in and if the pressure is high, which most of the time it is unfortunately, this will allow steam to work its way into the radiator.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Fred
    Fred Member Posts: 8,518
    edited April 2014

    I think Chrisj is correct in his assessment. The hissing and the drips of water you mention, certainly indicates a leak somewhere around that valve., either at the stem packing, the union that attaches it to the radiator or maybe even a small pin hole rusted through on the underside of the horizontal pipe. That is probably causing rapid condensation at that point and causing the hammering. Do you see any steam around that area when the boiler is running? Can you feel the underside of that coupling for moisture? The fact that the radiator still gets warm/hot even with the valve closed probably means the large washer inside that valve no longer seals completely. They do get brittle and decompose. Certainly excessive pressure can also be a cause but I would think that would affect at least some of the other radiators as well.Anybody else in the building experiencing similar problems?
  • brooklynquestion
    brooklynquestion Member Posts: 6
    Gorton No. D

    The air vent is a Gorton No. D
  • brooklynquestion
    brooklynquestion Member Posts: 6

    Hard to say where the hissing is coming from exactly, but it sounds closer to the packing nut. The small drip comes right beneath the union, though.
  • Fred
    Fred Member Posts: 8,518
    Tighten up

    Well, you can certainly take an adjustable wrench and tighten up the packing nut a bit and see if that gets rid of the annoying hiss. If not, you may need to replace the packing. You can try to tighten the union up a bit with a pipe wrench as well. Every once and a while I have one that will leak a little, I think from simple expansion/contraction over the heating season. 
  • moneypitfeeder
    moneypitfeeder Member Posts: 246
    edited April 2014

    The video you posted really makes it look like the inlet valve needs to be  repacked to stop the hissing. I wasn't sure from your posts if you understand how to remove and repack an inlet valve or not. If you need further assistance to repack the valve please reply, I think we can certainly tell you how to repack the valves joint , I've repacked several myself, but did not take pics... I'm sure someone on the wall might even have photos!
    steam newbie
  • brooklynquestion
    brooklynquestion Member Posts: 6

    Well I tightened up that packing nut and I think maybe the hiss is a little quieter though still very noticeable.

    Listening closely, I think the hissing is coming from where the stem meets the nut.

    Also, you can see in the attached picture the leak I witnessed after tightening up - looks like the seam is failing.

    I'm a total amateur just sleuthing around the internet, can I just duct tape some of this stuff up or am I going to actually have to get management to replace this whole sucker?
  • Greybeard
    Greybeard Member Posts: 6
    Don't Get Scalded

    Unless the original poster can confirm that the boiler is shut down and not about to start up, he should not attempt to repack the shutoff valve lest he get scalded by steam.   This is a job for the building superintendent, who can shut the system down before working on it.
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