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Where is the water in my boiler going?

My one-pipe steam heat system loses enough water that the LWCO feeds it weekly during the heating season. It did this before I replaced the old snowman conversion oil burner with a new Burnham gas unit a couple of years ago, and it still does, at about the same frequency, now.
There are no under-the-floor returns. Everything is visible, and there are no obvious leaks.
Is the system losing water at the radiator shut-offs? I don’t see that happening, but I can’t say that it’s not. Does anybody have a good technique for determining if one of them is the problem? Or is there some other place I should look first?


  • nicholas bonham-carter
    First overfill the boiler well up into the risers, and let it sit for a few hours. Then look in the fire box for any signs of leaking.
    Next look at the main, and radiator vents, and make sure they have closed after all the air has escaped.
    Check the packing nuts on all the steam valves for wisps of steam escaping, and tighten, or repack as needed.
    When the feeder adds water, is the water level ever too high? Pressures over one pound can push water out of the boiler into the returns, from which it returns when the burner cuts off. An accurate low pressure, (0-3 psi) gauge is an essential item in tuning your system.--NBC
  • New England SteamWorks
    New England SteamWorks Member Posts: 1,520
    edited September 2017
    Where is the water in my boiler going?

    -Same place your money is going: Up the chimney. Likely it's too late with that much water, but in any case, time to use "Find A Contractor"
    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
  • Fred
    Fred Member Posts: 8,542
    After the system is hot and the vents have closed,Use a small mirror to check the radiator valves and the vents. If steam is escaping the mirror will fog up.
    Also check to make sure all radiator valves are fully open. If only partially open, on a one pipe system, some water can be held in the radiators.
    When the boiler was installed, were the wet returns cleaned/replaced? Returns will get clogged and water can be very slow to return to the boiler but I would think at some point the boiler will be over filled, once it sits for a day or two. Make sure the wet returns are flushed out and open.
    Do you have a meter on the auto water feeder? If so, how much water is actually being added? There will be some "normal" evaporation.
    Also, is the probe for the LWCO installed in the correct tapping? If it is installed high, it may trigger and call for water after the boiler is producing steam. Again, I would expect the boiler to over fill relatively quickly.
    What pressure is the boiler running at? If the pressure is high enough, it can well cause some vents to leak and/or open allowing steam to escape.Keep the pressure at or under 1 lb.As has been said, put a low pressure gauge (0 to 3 PSI) on the system. Don't assume that because the Pressuretrol is set correctly that it is actually running at that pressure.
    New England SteamWorks