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New boiler, system leaking intermittently!

A little background:
In an old (100+yrs) 5 family apartment building the steam boiler failed after 9 years, the one before that also lasted 9 years; naturally this raised some suspicion as to why. It is a 1 pipe system configured as 2 pipes for the supply loop in the basement; at one point, apparently as a result of a change in the basement layout, one of the condensate lines runs under a door sill, other than that all condensate lines, mostly visible, run just above the floor.

The mystery:
for several days the boiler feed water/make up unit was, as it should be, idle. A metered feed unit was installed with the new boiler to insure this would be the case as the old boiler was going through a feed/run/shut off on low water cycle every 20 minutes before it was replaced. at this point, 3 weeks after installation the meter show 160 gals have been lost, but no leaks are evident. It also seems that the water is lost only while the boiler is actually running.

Greatly appreciate any thoughts on this.


  • nicholas bonham-carter
    Maybe an underground return leak?—NBC
    STEAM DOCTORJoeEngineerBobC
  • Jamie Hall
    Jamie Hall Member Posts: 23,675
    160 gallons in three weeks is simply insane. While that probably isn't a total consumptive loss, it's a lot. And you indicate that it seems to disappear only while the boiler is actually running? That suggests that the loss is from a steam line, since this is a one pipe system, or from a condensate line located above the water line in the boiler (please note: if the condensate line in question does not have a steam trap or a water loop separating it from a steam line, it is a steam line. There's debate on what to call it, but for our purposes here we are looking for a line to which either steam has direct access, or which carries condensate only when the boiler is running).

    You do not indicate the size of the boiler, nor the duty cycle. Both would be helpful. The steam loss you mention works out to the equivalent of 65,000 BTU of steam per day -- or, looking at it another way, close to 8 gallons of water equivalent per day. Or if you are running 10 hours per day, the equivalent of a decent sized radiator.

    Since I dare say you have looked for puddles -- and 8 gallons a day as water will create a puddle -- you are going to have to look for a significant steam leak (there is, however, the odd possibility which occurs to me of a condensate drip which is tied into a sewer line, rather than a return to the boiler. It's happened...). One would think a steam leak of that magnitude would be obvious -- but not necessarily. I really can't tell you where to look -- or what you are looking for (a missing main vent? A small pipe plug just not there? Top of a riser in the attic?) but I recommend you check every inch of steam main or condensate line elevated from the boiler.

    You need to find this leak, if only because it is costing you money in fuel. Never mind the wear and tear on the boiler.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 9,981
    Perhaps someone piped what should be a vent outside or up a chimney? Does someone have water spewing out a vent in an apartment somewhere they aren't telling you about?
  • ethicalpaul
    ethicalpaul Member Posts: 5,802
    It seems like it could still be in a wet return even though it's only noticed during the heating cycle.

    Due to the nearly useless and possibly harmful Hartford Loop, a wet return leak won't show immediately in the sight glass, and will only show up as the condensate refills the wet return line at the start of a call for heat making the observer think that the leak is happening during firing only.

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

    EBEBRATT-Ed Member Posts: 15,849
    I am not clear, is this boiler new or is it 9 years old?

    If you can't find any leaks shut the boiler down and manually fill it with water until you get water up above the top of the boiler and wait to see if it leaks. Look inside the combustion area if possible.

    Don't fill it with water while it is really hot. Drain down and start afterwords
  • mattmia2
    mattmia2 Member Posts: 9,981
    Here's another thought, what is the loss in a shorter period? Are you sure it started at 0 with the system filled and much of that isn't the boiler being filled or refilled as it was installed?
  • Fred
    Fred Member Posts: 8,542
    Has any skimming been done that might have flowed through that meter?