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Is my return wet or dry?

Motorapido
Motorapido Member Posts: 307
I have a one-pipe steam system in my house, parallel flow. My steam main and branch off the main both end with a step-down fitting into which a smaller diameter pipe is threaded, and that smaller pipe drops straight down until it hits a fitting that turns it into a horizontal pipe of the same diameter, which then gradually drops in height as it heads to the boiler. However, where that horizontal, sloped pipe reaches the boiler, it is still an inch or two above the lower-water mark on the boiler when it reaches the location of the boiler. The return line does not drop below the boiler low-water line until it joins a vertical pipe that drops down to the floor where it joins an an up-pipe that allows it to return into the boiler. The fresh water replacement feed line is connected at the top of a T where the condensate rises back up off the floor and then into a pipe that goes into the boiler.

My main and the branch off the main both have nice, big vents (two Barnes and Jones Big Mouths on the longer section, and a Gorton #2 on the shorter, immediately before the step-down fitting that then drops straight down through a smaller diameter pipe. I thought from the drop-down after each of the main vents, the return piping was entirely wet return the whole way back to the boiler.

But reading many postings on this forum makes me think that those return pipes are actually dry returns, since, although they are very low and sloped, they are not below the boiler water line until they drop into the boiler return pipe.

Do my main vents prevent ALL steam from entering those vertical, smaller return pipes? I think not, since they get pretty darned hot when the boiler is firing and I have steam pressure in the mains. I have not yet read the temperature with my digital infrared thermometer. To my fingers, they do not feeling as fiercely hot as the fittings onto which the main vents are attached, but when the mains are pressured, those returns are hot enough that I cannot keep my hands in contact with them for long.

Those return pipes are not insulated. I have read that insulating them prevents acid build up in the return water. But now that I suspect that they are steam and condensate filled, I have even more reason to consider insulating them.

So, do you believe that those lines are filling either entirely or partially with steam? If so, is this beneficial, if that steam pressure helps move the liquid condensate on its way back to the boiler? I should mention that the main return which is fed by drops from the steam main and a branch main are pretty long -- about 25 or 30 feet.

Bonus question for your consideration. I start to hear water movement in the return lines precisely when steam arrives at the main vents and closes those main vents. I presume this means that the new steam pressure in the mains is assisting in moving water back through the returns and on their way to the boiler. Is that a normal and good thing to hear, or should all of that condensate have gravity-fed itself back to the boiler long before the next steam production pressurizes the mains? I have not yet opened the return flush valve back on the floor by the boiler, and I do plan to open the return line valve sometime soon to drain out any crud, and perhaps to rig up an adapter fitting so that I can unscrew a vent from the main, put in (if such a thing exists} a close nipple that is NPT thread on one end and garden-hose thread on the other, so that I could thread a garden hose to the start of the return line, to push fresh water through the returns to help clean them out. Unfortunately, I do not have a valve at the condensate return pipe into the boiler to allow me to block dirty flushing water from entering the boiler, and I do not have a valve to prevent the hose water from backing up into the mains. I figure that is not a big deal, since I can then blow down the boiler, and future steam cycles will wash out any crud that pushes back up into the mains.

Thanks in advance for all insights and observations.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,344
    Posting pictures would be a big help
  • Motorapido
    Motorapido Member Posts: 307
    As a writer by trade, I turn an old saying upside down, and say that one word is worth 1,000 pictures. :p
  • Jamie Hall
    Jamie Hall Member Posts: 22,942
    If they are above the water line, they are dry returns. However, that said, I am inclined to wonder whether they are supposed to be. It wouldn't be the first time -- by any stretch -- that a new, shorter boiler had been installed at some point and lowered the water line, turning what had been wet into dry. Your main vents won't prevent steam from getting into them, however if they themselves are not vented, very little steam will get in there anyway, as the air can't get out.

    This may not be a problem in a one pipe steam system (in a two pipe system it would be somewhere between a problem and a catastrophe).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,542
    Wet returns need to be below the "NORMAL" boiler water line. That's the water line where the water should be when the boiler is idle.
  • Motorapido
    Motorapido Member Posts: 307
    Fred, that's interesting. I would not have thought of that on my own. I was thinking that for the return to be wet, it had to be running below the line drawn on the boiler jacket as the low water indicator -- as if the contents of the return pipe would care about lines drawn anywhere. Your logic makes sense, that the returns go wet when they are below the actual boiler water line.
    I will use a long level to mark a line out on the wall along which the return travels, transferring the middle/half-full point of the sight glass over to the wall where the return runs, to see if the return is beneath that marking. If the return line is slightly above the half-full point of the sight glass, should I use a level to transfer the height of the top of the return line over to the sight glass and use a Sharpie to make a mark on the sight glass and and then keep my idle water level slightly above that mark? That way, at least a portion of that long run of horizontal return could be below the water level, lessening the total length of that pipe into which steam would work its way. I bet the 1920s original boiler had a much higher water line than my 10-year-old Peerless gas boiler and my return line was positioned appropriately for the old boiler, but probably on the high side for this lower boiler. Ah, progress.
    Meanwhile, I think I would benefit from insulating the entire length of the return line just for good measure. I have no need for the warmth in the basement, since the basement of a 1920 house is not a place where I like to spend much time (except for when I am having fun studying and improving my steam system).
  • Motorapido
    Motorapido Member Posts: 307
    So if I did not care about the cost of pipe or the labor involved to lower the return, would it make sense to lower it so that starting at its highest point on its sloped horizontal travel it would be beneath the idle water level? Wonder what sort of efficiencies would be gained? Or should I stop over-thinking it?
  • Fred
    Fred Member Posts: 8,542
    edited January 2017
    The wet return should be below the boiler normal water line. Half below and half above will still cause some problems/probably noise. The wet return actually does not need to be sloped. It is all filled with water, up to the boiler water line and it will continue to normalize itself as new condensate drops into it. If you have to lower it, you may only have to take it loose at each end (maybe break or cut an elbow and add a nipple to the vertical on each end, a new elbow on the horizontal and a union to the new nipple to tie it to the old vertical. Be prepared to have to skim the boiler again though. You may be able to raise the boiler water a little but not too much. You want to leave a steam chest in the boiler.

    If the wet return is that high, do you have a proper Hartford loop? If you do decide to drop that wet return, drop it close to the floor and add a Hartford loop. That will keep water in the boiler should tthe wet return ever spring a leak.
  • lchmb
    lchmb Member Posts: 2,997
    I'm curious (btw I'd still rather see pictures.sometimes the best words dont convey what you dont know) but are you actually having a problem? Water hammer, unable to heat, uneven heat? Sometimes another old saying come's to mind "aint broke, dont fix it"
  • Jamie Hall
    Jamie Hall Member Posts: 22,942
    Indeed. Whoever it was who put that Peerless in ten years ago messed up -- not to put too fine a point on it. It should have been set so that it's water line matched the water line of the old boiler. It's a common enough error.

    The best thing to do is to grit your teeth and repipe the returns so that they are down where they belong. Close to the floor. As @Fred notes, the don't absolutely have to have a slope, although I prefer to have a definite pitch on them so that when you go to flush them out -- which should be done once in a while -- they will drain clear. Also, to facilitate that, where the verticals some down they should meet the horizontal lines with a T, not an elbow, and the T should have plugs so that they can be removed to make flushing the lines easier. You can probably tie into the bottom of that existing pipe you mention which goes down and then back up to the boiler. Find a diagram of a Hartford Loop to see how it should be piped.

    Copper is OK below the water line, by the way, and will likely be much easier to run.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England