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Hot water boiler, indirect water heater, oxide, leaks...

LadyXoc Member Posts: 1
A couple of weeks ago, my 5 year old boiler (hot water heat) started disgorging water through the relief valve (not to much, say about a quart per episode. So: called the plumber and they installed a new relief valve and pressure regulator valve, mucho dinero, and an expansion tank (though the old one was okay) which was too small and had to be replaced with one that is bigger than the one I had. At least they refunded about a third of the mucho dinero. But it was still mucho.
Anyhow, I guess the system was doing what it was supposed to do with the old equipment, because it is still doing it with the new equipment, except now there is black oxide in the discharged water.
The plumbers claim that I need to replace the 35-year old Amitrol - however for a test, I took the Amitrol out of the system and the boiler still sent out water through the new relief valve. There is an old leak in the pipe that goes to a bathroom, but it was never active until I had a guest who took a shower there - and afterward there was about a quart of water on the basement floor under the leak - full of black oxide.
I should mention that all the radiators in the house were converted from steam to hot water, at least 50 years ago, and tend to be cool on the bottom, maybe from sludge?
Is there any hope, or should I just start over with electric?
Thanks for reading!


  • Jamie Hall
    Jamie Hall Member Posts: 23,650
    Have to admit to being slightly confused. How is it that a guest taking a shower managed to open a leak in a heating pipe? Or am I missing something?

    In any event, the presence of the black goop suggests rather strongly that you need to flush the whole system thoroughly. Very thoroughly. Then add new water with a corrosion inhibitor.

    When you get it flushed, make sure that the connection to the expansion tank is completely clear -- may have to flush that separately.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,476
    An Amtrol indirect tank? Yes if the coil may fail you may get city water pressure to the boiler. I suppose some boiler crud could cross to the potable water, I’ve seen it happen in glycol systems when tank coils fail

    30 years on a tank? What’s in your wallet 😂
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream