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Radiator shut off valve and boiler sight glass

Hi all,

Just moved into a house and am getting familiar with my gas-fired steam boiler. Couple of questions:

1. I've been trying to save on the gas bill by shutting off all the radiators upstairs during the day. In the back bedroom (which we never go in anyway) there's a radiator that seems to fill with steam even when the shut off valve is turned all the way clockwise (see picture). It's also unique in the house in that you can only turn it about 3/4 of a turn. The rest of the valves in the house need several full turns to fully open or close. What's the deal with this valve? I don't feel like heating a room that we never go in.

2. The boiler sight glass is filled up to 1/2 with water. About a 1/4 of the way up the sight glass is filled with rust colored water (see other picture). A few times I've drained the boiler to just below the bottom of the sight glass and filled it back up with fresh water, but the dirty water returns. Is this something I should even bother with? I have a probe type low water cutoff.

Thanks in advance.


  • JStar
    JStar Member Posts: 2,752

    I would advise you to keep the radiators on even if you don't use the rooms. A cold room will only make the other rooms colder, and run the boiler longer. Plus, with radiators shut off, the boiler will be grossly oversized, causing short cycling, wet steam, and extra wear on parts.

    The boiler should be drained a few cups every week. If the water is clean, go every 2 weeks. When you refill the boiler, run it long enough to make steam to boil out all of the fresh water's extra oxygen. The sight glass can be removed and cleaned.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,288
    One pipe or two?

    If your system is a one-pipe steam system you can turn off the radiator by turning the vent upside-down, assuming the vent works. It's not unusual for the valves to go bad, but rather than replacing it now you can just flip the vent and deal with it in the spring.

    If you have a two-pipe system, the radiator won't have a vent, but it's a little hard to tell what you have because the valve in the picture doesn't look like a typical one-pipe radiator supply valve, and the pipe looks smaller than usual, but it's connected at the bottom, which is typical of one-pipe.

    It's normal for boiler water to contain some rust, and draining it and replacing it with fresh water only does more damage to the boiler. If you add fresh water to a boiler you should always bring it to a boil immediately to drive off the dissolved oxygen.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Saving money

    If this is a 1-pipe system, then the valves must never be closed, as they will always let a bit of steam into the radiator, which will condense and not be able to drain out. When you turn the radiator on again, a geyser of water may shoot out of the air vent making everything wet. If you have Hoffman 40 radiator vents, you can turn them upside down, and that will prevent the air from leaving the radiator, effectively turning them off. A thermostatic radiator vent will accomplish the same thing automatically.

    While you are looking at the economies of operation, examine your main vents, and tell us what you have. If your radiator vents can be heard, then it's a sign that you are buying extra fuel to pump the air out of your boiler and pipes.

    Use setbacks for long periods of time to avoid using extra fuel. Most people are more comfortable at a lower constant temperature than a variable range from above normal to below normal. Just as keeping a constant speed in a car burns less fuel than speeding up and slowing down, so the thermostat should be "set and forget", unless you are away for a week. Checking your system pressure will also contribute to fuel economy, as going over a few ounces is a waste.--NBC
  • DaveZR2
    DaveZR2 Member Posts: 3
    edited December 2013
    main vent???

    Thanks for all of the replies. I've stopped playing around with the shutoff valves.

    To answer one question: I have a one pipe system.

    I've attached two new pictures showing the boiler and the piping above it. I do not see a main vent. I'm assuming it would be located in this area. The close-up picture shows what looks to be a 1" plug. Would this be where the main vent used to be?

    To answer another question: Yes, I can hear the radiator vents occasionally.
  • DaveZR2
    DaveZR2 Member Posts: 3
    Will this work?

    Can I use this where the plug is in my last post?
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