Gravity Return vs Pump return

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GrockMan
GrockMan Posts: 1
in Strictly Steam

Background:

  • I've been talking with many contractors to try to get my steam boiler replaced for my giant 7000 sq.ft. house with 30 rads, and hopefully made it more efficient and less likely to fail in only 20 years.
  • My 1998 condensate pump has had an issue of running continuously, thereby flooding the boiler to the top, thereby accelerating rusting and cracking. We opened up the wiring boxes to find that the condensate pump is NOT connected to the boiler's sensors in any way, despite clear correlation with blowing down the boiler on the one sensor's side (first image) remedying the condensate pump.(And according to several contractors so far, the main pipe size is too big compared to the return pipe size to consider hydronic without a massive overhaul.)


Question:

A few contractors I'm talking to are recommending omitting the condensate pump and just using gravity to return the condensate to the boiler. Others suspect that would not be a good idea, thinking the pressure would not be enough or there would be too much condensate buildup in the wet returns that might make them burst or leak perhaps.

What do you all think?


(Any other advice for this project would be massively helpful. I am very new to this, but learning fast. I got some of the holy books, have not read them yet.)

Equipment:

  • Weil-McLain LGB 5 Low-pressure Steam Boiler: installed 2001
20260917_115344.jpg 20260917_115353.jpg image1.jpeg image3.jpeg
  • [DISCONNECTED ] Sterlco - Sterling inc - 1/3 HP Pump??: Installed 2001, same day as boiler. Looks completely defunct and gutless
IMG_1021.jpg IMG_1022.jpg IMG_1023.jpg
  • Smaller condensate pump: installed 1998 - but still connected (didn't get the make/model)
Screenshot_20261016_133543_Gallery.jpg Screenshot_20261016_133554_Gallery.jpg
  • Wet return, running below the boiler, feeding into the boiler, running through about half of the basement
  • Dry returns running parallel to the main pipe throughout the whole basement, feeding into the wet return

Comments

  • mattmia2
    mattmia2 Posts: 18,190

    the pumped vs gravity return has to do with the water content of the boiler. If the system has too much of the water from the boiler in the system in the form of steam while the system is running, the water level in the boiler may fall too much. bigger boilers have more water content but modern boilers have less water content than older boilers did. if the boiler doesn't have enough water content, more volume can be added with pieces or large pipe or a passive tank that is set up as a reservoir. Usually there are better options than a pumped return.

    the other reason to have a pumped return is if you have emitters below the boiler so that the condensate can't return by gravity.

    Where are you located, there may be some pros here that are nearby.

  • Jamie Hall
    Jamie Hall Posts: 27,883

    Lose the condensate return pump and rely on good old gravity. The only reason why you might not be able to do that is if the piping is such that somewhere a wet return is above the water level in the boiler or if there is a radiator which is below the water level in the boiler.

    There is a possible pressure concern as well. If this is a true two pipe system, any dry returns must be high enough above the boiler water level so that they don't flood. I can't tell from the photos whether or not this is the case. This is not usually a problem, but easily checked.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Ironman
  • EBEBRATT-Ed
    EBEBRATT-Ed Posts: 21,126

    Post your location.

    You need someone that knows steam well and there are not many that do. You don't want this to turn into a horror show.

    mattmia2Ironman

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