Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Why would condensate not be coming back to the boiler in time to stop low water shut off?

I had my plumber do a seasonal boiler service and run a full system test by running the boiler until all radiators heated up. After about 2-hours, after which all the radiators still hadn't fully heated up, he aborted the testing for two reasons. First, condensate wasn't coming back to the boiler fast enough leading to low water shut off cycling. Second, he said my automatic water feed wasn't working. The following day i ran a system test myself, turning the thermostat up to 90 degrees and adding water to keep it from going to low water shut off. After about 2-hours, with everything heated up, and the system finally getting to about 1.5# of pressure, i heard a hissing from the right hand rear side of the boiler near the Hartford loop. I called my plumber to let him know about the hissing and now he's concerned i may have a leak in the boiler (it is only 11 years old.).

What can cause condensate to not come back to the boiler in time? (I only have 19" for my "A" dimension, can this be the reason?)

How can I determine if my boiler has a leak?


  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    You need a good steam tech. First off, it shouldn't take two hours to get the radiators. 20 minutes, maybe. Not two hours. So there's something very wrong just there. Second, at 1.5 psi, 19 inches is nowhere near enough A dimension, though where the water may have wandered off to as a result would depend on how things are piped.

    Slow returns are another matter altogether.

    The hissing might be a leak. Might not, too. What else is in that vicinity? A vent, perhaps?

    And, of course, you may have a leak. They come in two flavours. If the leak is below the water line of the boiler, it will show up as the water level dropping -- perhaps not that fast -- down at least to the level of the Hartford Loop. If it's in a wet return, it will stop there. If it's in the boiler, it will keep going until it gets down to the leak -- and you may or may not see a puddle. If it's above the water line, the most obvious clue is that you have to add water to the boiler -- but with your slow returns, you will have to have patience, Since you seem to have to add water to the boiler while it is running to keep it running, what you will need to do is to note the water level when it is cold. Then run it for a while. Then let it go old again, for several hours, until you are reasonably sure that the condensate has returned. Then check the water level again. If you added water during the run, the water level should now be above where it was when you started.

    But I think you need a competent steam guy to look at this. Multiple problems -- which you clearly have -- are hard enough for a pro. to diagnose, never mind a homeowner. Where are you located? We may know someone in your vicinity, or you could check the "Find a Contractor" tab, though not everyone is listed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • (I only have 19" for my "A" dimension, can this be the reason?)

    Yes :)

    Except presumably it has worked in the past? If it takes two hours to heat the radiators I'd say there's not enough steam in the system to make any condensate to return.

    Might want to look for a lot of steam coming out of your chimney, unless you have some buried returns.
    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
  • mickeylewis123
    mickeylewis123 Member Posts: 45
    edited November 2020
    I'm in Englewood NJ
    I had a steam expert in a few months ago. His proposal was $ worth of re-piping work - the near-boiler piping and return piping, and install a 2-stage gas valve to enable low firing. I thought that was a lot of money with no guarantee of fixing my problem - which to summarize is very high fuel costs in the winter and the boiler taking one and a half hours to heat up all 16 of my radiators (some heat up in 20 minutes, some 40 minutes, a couple 90 minutes.)
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    No prices. Please.

    That said, from your description it is evident that your system is operating very poorly indeed, and does need some qualified attention.

    You really do have a choice: either get the thing corrected, or live with poor heat and high fuel bills. Take your pick.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SlamDunk
    SlamDunk Member Posts: 1,580
    Post a few photos from afar and different angles. For the leak, turn off boiler, and over fill it. If there is a crack, you will have a puddle on the floor. Sorry for your troubles. Some boilers actually do leak after ten years. You can search this site for more discussions about that.
  • underdog32
    underdog32 Member Posts: 91
    You don't say if it's a one pipe or two pipe system, but I've been fighting an issue like this for a few days on my two pipe system. In my case, the wet return was very clogged. I did not repipe, but i did tear it apart and flush it till i had good flow.

    The second problem, still not solved, is that water is waterlogging my supply pipe, due to what I believe is a bad f&t trap not letting water escape to the return.

    I'm not a pro in any way, this is just my experience with a similar problem.
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    I am always highly skeptical of the allegation of “condensate slow to return” in a residential boiler. I’ll bet my hat that it’s actually boiler water getting carried over into your mains.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • Precaud
    Precaud Member Posts: 370
    In my case it was caused by a clogged wet return following years of neglect.

    1950's Bryant boiler in a 1-pipe steam system at 7,000 ft in northern NM, where basements are rare.