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Boiler Keeps Filling With Water

Yanks2009 Member Posts: 20
Hi Everyone,

I have an old Crane steam boiler that keeps automatically filling with water.  The boiler has been shut down for the summer but it seems as though the automatic water feeder keeps adding water.  I have to drain the boiler every week because so much water has been added that the sight glass starts to drip.

Any suggestions as to why this is happening.  FYI, I do not know much about boilers.



  • Boiler Flooding

    Hi- Depending on how your boiler is configured, there maybe more than one source for the added water. As you mentioned, one source could be your automatic water feeder and another source maybe the domestic hot water coil if your boiler has one installed. These coils can develop a pin hole leak and flood your boiler.  You can determine which item is causing the problem by shutting off each individual water source. If you don't have much experience in this area you might want to take a look in the "Find A Professional" section at the top of this page and see if there is a steam pro located near you.

    - Rod
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,285
    Tell us about the feeder.

    Model number?
    Retired and loving it.
  • Dave in QCA
    Dave in QCA Member Posts: 1,777
    edited June 2010
    Leady Fill Valve?

    Another possibility....

    I have seen older McDonnell & Miller models develop a "leak by" problem.  They would slowly leak water through the valve, like a drippy faucet, and the boiler level would slowly creap up. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • Yanks2009
    Yanks2009 Member Posts: 20
    M&M No. 101

    Thanks for the replies.

    You may be right, the feeder is an old McDonnell & Miller No. 101.  More than anything, it's an annoyance b/c I have to flush the boiler more often.  I'm trying to hold out for another year or two and then upgrage the boiler. 
  • Water leak

    Hi - Have you definitely determined that the water feeder is the item that is leaking? You do this by shutting off the water to the water feeder. If that stops the rising water level in the boiler then your water feeder valve is leaking.

    If after shutting off the water line to the water feeder, the level in your boiler still rises and if you have a coil in the boiler that make domestic hot water of the sinks,showers etc., it may mean that this coil has developed a pin hole leak and is leaking water into the boiler.

    Having "new" fresh water constantly added to your boiler can cause a BIG problem. It contains excess dissolved oxygen which can cause rapid corrosion in your boiler. When you add "new" fresh water to your boiler you should always heat the boiler water to a boil so the excess oxygen is driven off.  You need to find the source of the leak and fix it or have it fixed.

    Here is a link to the manual for McDonell Miller #101A which maybe of help to you, Rebuild parts are available.


    Since you're considering a new boiler you might also want to check out the Hydrolevel VXT water feeder. It has a lot of superior features such as a counter so you can keep track of how much water is being fed to your boiler.


    - Rod
  • Yanks2009
    Yanks2009 Member Posts: 20
    No coil

    Thank you.  I forgot to mention that there is not a hoter water coil...I have a separate water heater.  I have tried to shut the water off to the water feeder, but it does not help, so maybe the water feeder isn't the problem.....
  • Excess Boiler Water

    Hi-  With no water coil it has to be the feeder unless you can think of another water source that might be putting water in the system. Do you have away of definitely isolating the feeder? If so try that.

    - Rod
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