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Why is my boiler still flooding?

I have a single pipe steam system with a powerflame burner and a McDonnell Miller water feeder.  The boiler kept needing to be drained down as it seemed to be overfilling.

I shut off the valves and isolated the feed control which stopped the problem.  I then changed the guts of the feeder with new replacement parts.  Now it is happening again.  Are the parts bad or is it that the feeder itself is leaking? Weird?


  • JStarJStar Member Posts: 2,752

    Does the water feeder activate, adding water, or does it leak past in its own? Do you know the water pressure in your house? Is it high?
  • Auto/over-feed

    Turn off the water supply stop valve to the feeder, and watch the boiler as it fires a few times. Is there enough movement in the waterline to activate the lwco? Very dirty water can surge so much that the waterline moves quite a bit. Bad supply, and return piping can do the same thing, as can steam pressure which is above 1.5 psi(don't rely on the useless 0-30 psi gauge which came with the boiler, but instead get a 0-3psi gauge from gauge
  • RodRod Posts: 2,067
    Internal Hot Water Coil?

    Hi - Does your boiler have a internal coil for heat domestic hot water? If you have one, it may have developed a pin hole leak which could be the source of the extra water. Water can only enter the boiler via the waterfeeder line or if applicable, a leaky internal hot water coil.

    - Rod
  • JEMM55JEMM55 Member Posts: 47
    internal coil

    I thought of the coils but when I isolate the LWCO it does not flood.

    Only when I let the LWCO back into the system does it flood.
  • RodRod Posts: 2,067
    Flooding Problems

    Hi- If the HW coil tests out okay then the problem is definitely related some how to the LWCO makeup water circuit.'


    1. If the boiler is left standing cold for several days, does the water level in the boiler rise?  If so this would indicate a problem with the fill valve or electrical sensors in the LWCO/makeup water circuit.  You should be able to further isolate the water valve by disconnecting the power leads to the valve. If it still leaks water then it is probably a valve problem. (sticky valve ,bad valve seat etc.)   If the leakage stops and then starts up again when the wiring is reconnected then you probably have a problem with the LWCO switch setup or in the power connections.

    2. If the flooding occurs when the boiler is operational, it maybe due to the slow return of the condensate which then causes the activation of the LWCO water feeder.  If the condensate is slow returning to the boiler then you need to check out the wet return as it may be clogged up which is restricting the prompt return of the condensate.

    JStar ask you if your water pressure was high. I assume he may be considering another possibility that if your water pressure is very high it might be overcoming the water valve so you might want to check your water pressure.

    - Rod
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