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Boilers Waterline when off

Jim_35 Member Posts: 10
water level be in a steam boiler whens its off?? Somebody told me to fill it all the way to the top so that you dont get a corrosion line and scale buildup (like at the docks) and Ive also heard to completly drain it out by filling and flushing it a few times and then leave the valve open until the heat season begins.

So whats the verdit?



  • Ken_8
    Ken_8 Member Posts: 1,640
    That depends...

    If a commercial boiler, the duration of the "off period" may impact how the boiler gets "laid up."

    If residential, we typically do nothing except suggest draining, washing out with TSP, rinsing and that leaves a trace high (anti-rusting chemical state) pH within the water.

    I have heard all the advantages of flooding and/or draining a steam boiler for the 4-5 months of summer - but seen more boilers over 40 years old that never any such thing to validate the claim.

    The problem of flooding the boiler is that someone must remember to drain it to the NOWL before a sudden call for heat occurs in fall.

    Bottom line? The benefits derived from simply cleaning the water side immeditaely after the heating season is over, are better than flooding the boiler - which at best is margiinally effective at prolonging service life.

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  • laying up the boiler

    After the water sides of the boiler has been cleaned properly fill the boiler with fresh water to the appropriate water level and add your chemical tratment.

    Fire the boiler until steam is produced to drive out oxygen and other dissolved gases. Then shut down the boiler for the shut down period.

    Personally, when the boiler is my resposibility I do what I was taught in the Navy. I fill the boiler to the top and leave it sit until I turn it on for the comming heating season.


  • Fred Harwood
    Fred Harwood Member Posts: 261
    Boiler summer care

    Here in western Mass., where my sainted Mother once said that she had seen frost in every month but July, that rare domestic heating call all but precludes turning off the boiler. Also, with direct DHW, the boiler must run anyway.

    With separate DHW, cleaning the fireside early, before the humidity gets to the cold soot and sulfur, works well before shutdown. With direct DHW, raising the water level to an inch or so above the coil helps to ensure capacity and spreads out any possible waterline corrosion effect.

    What have others found out?
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