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Finding the leak in steam system

tfahlbergtfahlberg Member Posts: 20
This winter I started having to add water to my boiler every few days. In past winters, I only needed to add water every 2-3 weeks.

I had my plumber out and two steam heat specialists. Its a big house building in 1886, with a large boiler, 15 radiators and a finished basement. They opened up the boiler cover, overfilled it and found no leaks. They checked all the radiators and found no leaks in the plumbing. Since some of the vents were old, they suggested that I replace them, which I did (Hoffman 40), and I also replaced the single main vent (Hoffman 4A). Half of my radiators are single pipe, and half are two-pipe. None of them have traps. All have vents.

I am able to see about 75% of the mains and found no leaks there. I can only see about 10% of the returns, so I poured measured amounts of water into six of the farthest radiators (via the vent hole); all of it returned to the drain valve (on the return side of the Hartford loop).

I'm about to have a feed installed to avoid the nuisance of adding water, but I would prefer to find the leak. Any suggestions?



  • mikeg2015mikeg2015 Member Posts: 498
    Try an infrared camera while it’s running. Some steam leaks remain invisible an don’t condense on the piping while leaking. Might only leak when hot or at pressure.

    I lose about 1 gallon a week and all are invisible.
  • Big Ed_4Big Ed_4 Member Posts: 1,095
    Are any of the return piping buried ?
    I have enough experience to know , that I dont know it all
  • Mike CascioMike Cascio Member Posts: 119
    That main vent is TOO small. Please post some pictures of the boiler, near boiler piping, closeup of the pressuretrol, and steam main. Is there only 1 main vent?
    If you have buried returns, its likely that they are leaking.
  • Danny ScullyDanny Scully Member Posts: 1,037
    Where are you located?
  • AMservicesAMservices Member Posts: 396
    You can use an air compressor and pump 5-10 psi, then spray radiator valves, pipe joints, ect... with soap.
    You have to plug all the air vents first and I'd take off the pressuretrol.
    Ive tested several systems that way and most of the leaks I find are at packing nuts.
  • SteamheadSteamhead Member Posts: 12,536
    I bet the leak is in the boiler, and the steam is going up the chimney.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Have you overfilled the boiler yet?—NBC
  • tfahlbergtfahlberg Member Posts: 20
    Thank you all for your questions and comments. I've been obsessing over this and it's nice to get some other eyes and brains on this. I attached photos below and have a few more to upload.

    I live in Lowell, MA. Yes, we overfilled the boiler twice, once with the cover on and once with it off. We sat and stared at the boiler fins for a while but saw no seepage. We didn't pressurize it with it open because we didn't have an easy way to vent it.

    I don't know if any sections of the two returns go underground, because most of the returns are behind the walls. I have pulled out some sections of drywall to check and the returns there were about 2' above the foundation.

    As you can see in pictures there are two mains and two returns. I believe you that the main vent is too small. Just to be clear, the "main" vent is actually just below where the left main starts to slope back down. I also see a piping stem about 8 feet away from the boiler that has been capped and where I could add antlers or something. I'll add some pictures of this.

  • tfahlbergtfahlberg Member Posts: 20
    I should add that all the radiators heat. It takes them a while but eventually they all get warm.

    I ran the system for a couple hours tonight and lost about 2.5 inches of water in the glass. By that time the wet returns must have dropped below the Hartford loop because when I turned on the water to refill the boiler it took a minute before the level in the glass started to rise.
  • Changing out the main vent for some decent main vent(s) may make a difference, as would correcting the bad supply piping. At any time while firing most of the water must be up in the mains.
    A faulty vent will not only increase the time for steam to push the air out of the way, but also allow longer durations of vacuum to hold the water up in the dry returns.
    When you overfilled, did you leave it full for a couple of hours to check for leaks?
    What is your pressure?—NBC
  • tfahlbergtfahlberg Member Posts: 20
    Thanks NBC.

    When you say to change out the main vent, are you suggesting I change the Hoffman 4A for something bigger in the same location? (Did you see the picture of it in the second set of photos?) I was thinking of adding another vent on the currently capped pipe that sits 8' from the header. (The second set of pictures shows that pipe.)

    Btw, only the left main is vented, as far as I can tell.

    I did not leave the boiler over-filled overnight. I'll try that. That will also show if I have any slow leaks in the returns.
  • tfahlbergtfahlberg Member Posts: 20
    NBC, what did you mean by "correcting the bad supply piping" ?
  • JUGHNEJUGHNE Member Posts: 5,120
    I believe I see 2 "pipe traps" in your return piping.
    The first must be a water seal for the 2 pipe vented rads that have their returns dropped below a water line.
    The second is below the HL tee and where that line connects to the boiler.
    Have those been opened and cleaned?
    These would always be full of water (and probably sludge).
    They could be causing slow return.....and your water fill looks to be connected into the first "trap/loop". It has happened that the water fill inlet gets partially plugged from the sludge, will flow some fresh water into the system but just enough to syphon or push the backed up water in the return into the boiler.

    Perhaps you are not adding as much water as you think but merely coaxing existing water back home.

    I know, sounds crazy.

    Is all of your basement floor the same level or is the boiler in a sub basement.....lower room?
  • Big Ed_4Big Ed_4 Member Posts: 1,095
    Gauge glass is clean and system loosing water . I suspect an condensation leak , looks like the returns are above ground from photos given ... Any place they may have to drop into the floor like outside entrance or walkways , Are there any crawl spaces ? Your loosing a lot of water and an bad steam leak you could not miss . You already checked the boiler for leaks ... Looks like sections of the return were replace and repaired already ..
    I have enough experience to know , that I dont know it all
  • Jamie HallJamie Hall Member Posts: 9,326
    You mention that you overfilled the boiler and looked for seeps... did you look inside the firing chamber? Or just outside? Boiler leaks are commonly between the steam chest -- just above the normal water line -- into the firing chamber. They don't show outside the boiler at all.

    They often will show, though, in the form of a lovely plume of steam out of the chimney...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Two risers come out of the boiler, (what size are those pipes). They connect to the header on both sides of the takeoff to the main, with the equalizer on one side. As the steam rises up out of the boiler, the two streams will collide, and send too much water with the steam up into the main.
    The factory specified piping groups the risers together, followed by the takeoff to the main. finally the equalizer is on the end of the header, dropping down to the Hartford loop. All the steam and water should travel in the same direction in the header, so that the water can be emptied by the equalizer, which can't happen with everything travelling in different directions.--NBC
  • FredFred Member Posts: 7,264
    Also, that Tee that goes to the equalizer looks like it is reduced on the horizontal which means the water can't drain out of the header until it is at least fills the header 1/3 to 1/2 way up and even then the water in the lower portion of that header can never drain through the equalizer. It has to run back down the boiler risers.
  • JUGHNEJUGHNE Member Posts: 5,120
    edited February 2018
    There is not much right with the boiler piping,
    Steam take off between boiler risers.
    Bull headed steam mains.
    Concentric reduction on header to equalizer.
    Hartford nipple quite long.

    But none of this would cause a sudden increase in water consumption.
    If the boiler is leaking then the owner should be aware of the piping problems and have them corrected with new install.

    With all the pipe issues there should be a lot of water hammer and wet steam..........those problems were not mentioned.

    PPS: the header almost looks sloped in the wrong direction amplifying the issue with the concentric reduction to the equalizer.
    So many "sins" of piping and it sort of works, how about that?
  • tfahlbergtfahlberg Member Posts: 20
    Thank you guys for the detailed comments which have been great. I'll try to answer your questions:

    The pressuretrol cut-in is set to 0.5 and the differential = 1. That appears to be working more or less correctly, since if I leave the system on long enough, it will cut out, and the pressure gauge will have moved up 1-2 ticks. I know I need to get a lower pressure gauge to get a more accurate reading, but it's in the ballpark.

    The risers are both 2.5" (O.D.) and the equalizer is 2.0" O.D. The mains are 3.5" OD.

    jughne, I wasn't sure what you meant by the two traps. Here's another picture:

    I did not remove the clean-out at the left end of that section for fear of a rusty water mess. However, when I poured water into the rads serviced by the left return the water was able to make it back up the right return to the spigot:

    I don't know if this picture is clear enough but those two pipes are the returns and the closer one has the spigot. Because the test water on the left return was able to come back up through the right (closer) return, I assumed that both of them were reasonably open. But I do get what you're saying about water getting trapped by sludge and the filler pushing it to the boiler.

    The basement is all the same level, and their are no rads in the basement. The boiler sits on the foundation, not sunk in.

    Big Ed, I think you're right that I would not miss a steam leak this big in the piping. If steam is leaking in this quantity it would probably be through the boiler. I don't believe the returns drop into the foundation. I don't think they would need to since there are no rads in the basement.

    Jamie, my plumber and I looked at the chimney exhaust and it was white, but it was below zero that day, so we couldn't tell if it was steam or normal condensate. I can't tell the difference. I'll take another look this weekend when it won't be as cold. I'm also planning to buy a nice long piece of clear tubing to use as a sight tube when I overfill the boiler for another test.

    NBC and Fred, I think I understand the problems with the construction. Good to know, especially if I have to replace the boiler. But the system only started losing larger quantities of water this season, so there must be something else going on.

    There is no water hammer nor wet steam out of any rads. I'm sleeping in the basement and hear some expansion when the boiler turns on, but it's not really hammer. I had a lot of hammer when I first bought the house, but got rid of it by lifting and leveling a few sagging rads.
  • tfahlbergtfahlberg Member Posts: 20
    So this weekend, this is my plan. Please tell me anything else I should do. Thanks!
    1. Buy a 6' clear hose as a sight glass, overfill the radiator by a couple feet and let it sit overnight - check in the morning
    2. Order a larger vent for the main near the boiler. Any suggestions as to the model?
    3. Pressurize the system at some point and try to figure out what is coming out of the chimney.
    4. Anything else?
  • At least one Gorton #2 for each 20 feet of steam main to be evacuated would be adequate. Also use the clear plastic tube to see what your pressure is doing when firing. I suspect you will be surprised when you see the water rise in the tube!—NBC
  • JUGHNEJUGHNE Member Posts: 5,120
    What I meant by the 2 "pipe traps" was in reference to the horizontal pipe under your returns/fill and the horizontal part of the lower Hartford Return where it connects into the return port of the boiler. By necessary design these are the low spots for returning condensate water. Just like a P trap under the sink.
    Sludge and mud may collect there. Which is good as it would keep a lot of it out of the bottom of the boiler.
    However it is good to have clean outs or drains at those points for periodical inspection and cleaning.

    This weekend before you overfill the boiler, perhaps you could check the fill flow by draining the boiler water out with the valve at the boiler return (this would be the yellow handle ball valve right at the boiler.....not the hose bib on the copper return.)
    Then with that open you could turn on the manual water fill valve. If you get a healthy flow of water (it will also be trying to fill the boiler) then your piping between those points is reasonably open.
  • tfahlbergtfahlberg Member Posts: 20
    edited February 2018
    NBC, let me make sure I understand what you mean. I was planning to attach the plastic hose to the yellow handle ball boiler drain valve and raise it up to see the water level when I overfill the boiler.

    Are you saying that before I overfill the boiler I should turn it on to see what happens to the water level in the tube? I can do that, but why would that be any different than watching the glass tube on the side of the boiler?

    I often watch the glass tube while the boiler is running. As the water heats the level always goes down and churns a bit. When the boiler shuts off maybe the level in the glass occasionally rises a little, but there are times when I don't see the level rise at all after the boiler shuts off.

    Would a slow leak in a wet return explain my symptoms? I assumed that because the water that I poured into the radiators made it down to the drain, the returns weren't leaking. But that seems like a wrong conclusion. Maybe the water made it down because it came down fast. If there were a small leak in one of them then condensate could leak out slowly even when the boiler was off. And once the return level falls below the HL, then it can't get back to the boiler.

    It should be easy to test this hypothesis. When the weather warms up I can fill the boiler and let it sit for a day or two without running. If the water level drops to the top of the HL, and no water appears around the boiler, then a wet return is probably leaking. And if that happens, then I should also be able to attach a hose to the drain valve and hold it up. The level at which water starts to come out of the hose should be the height of the leak. Make sense?
  • The plastic tube will show you the effects of pressure in the system: the water level in the tube will be the same as the water level in the wet returns. The tube should be atatched to the boiler drain valve, and not the float LWCO drain valve.
    You can see the importance of height of the dry returns. If they are too low, or the pressure too high, water will rise up into the dry returns, and prevent the main vents from letting the air out, as they will be blocked with water.—NBC
  • tfahlbergtfahlberg Member Posts: 20
    I'm sorry NBC. I don't understand which valve to connect to. Here are the valves I see:

    Yellow valve on left side of boiler.

    Drain valve on right side of boiler:

    Return drain valve (underneath the right return, with hose attached to it):

    To measure the height of the water in the wet return, wouldn't I just connect the tube to the return drain valve?

  • Jamie HallJamie Hall Member Posts: 9,326
    Take your pick -- they'll all be within inches of each other.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • tfahlbergtfahlberg Member Posts: 20
    Yes, as long as the water level is above the HL. I'm considering a situation where a return could be leaking and fall below the HL. Then the levels will be different.
  • JUGHNEJUGHNE Member Posts: 5,120
    edited February 2018
    One older boiler I service I check for leaks by removing the pressure relief valve and then use its drop pipe screwed into that opening. One could slip a foot or so of clear vinyl hose on the upper end.

    Then fill to the top of that pipe. In my case it gets the water level up to about 6'. For you the clear tubing could be observed if water drops.

    Also allows inspection of the bottom of the PRV.

    72" of height would give you 2.57 PSI on your returns.
    Should be enough height to flood all wet returns and provide more pressure than they would operate at.

    However how you overfill you may have an air bubble in the top of the loop at the returns, this may have to burp the air thru your fill pipe.
  • tfahlbergtfahlberg Member Posts: 20
    edited February 2018
    I'll be damned. NBC, you were right. With the boiler running, and also running low on water, I connected the green hose in the picture to the return drain valve. I had to lift the end of that hose 5" ABOVE the top of the HL before water stopped coming out. I couldn't believe it.

    When the boiler shut itself off for low water I listened carefully to the condensate flowing through the pipes. There was a lot more water coming down from the mains, than were coming from the returns. So maybe sludge is blocking that HL area after all.

    I'm going let the boiler cool down now and do the test that jughne suggested and check the flow between the filler and the boiler drain (w/yellow handle).

    Thanks again.
  • Either the return drain, or the boiler drain will work for this experiment.
    It will show how important low pressure is in the system, (during venting, and steaming phases), and by measuring the difference in height of the boiler waterline, and the hose waterline, will give you your operating pressure, using the formula of 1.75 inches per ounce of pressure. If the water rises more than 3 inches, you need more main venting.
    If you put an extension nipple on the prv port, and fill it up to the top of the nipple, and water loss can be seen later when the water is below the top of the pipe.—NBC
  • tfahlbergtfahlberg Member Posts: 20
    edited February 2018
    Ok, I back-flushed through both drains. It was pretty muddy at first through the boiler drain, so I kept at it until it was clear. The return drain was clear from the get-go because I had already drained the returns a couple times.

    Tonight I'll overfill and test for leaks overnight. If nothing leaks out, then I'll re-pressurize and check the height difference.

    Clearly I'm going to need way more venting. The main on the left is 60 feet long from the boiler to where the main slopes back down. Should I fashion an antler with three Gorton #2 ? Is there something else bigger and simpler with a 3/4" opening? (The Gorton #2 wants a 1/2"). What about the Barnes & Jones Big Mouth? (Although I don't know if anyone around here stocks it.)

    The main on the right is about 20' long before it disappears into a wall that I cannot penetrate. I looked everywhere that I could and did not find a vent for that main. Do I add a fourth Gorton to the left main to compensate?

  • JUGHNEJUGHNE Member Posts: 5,120
    This question may not necessarily concern your water use mystery, but would clear up something about the operation of your system.
    Concerning the 2 horizontal steam pipe mains above your boiler:
    Do they slope down hill away from the that the high point of the steam main piping. Or does one side go up and one side go down for slope?
    I see what could be drips off the steam mains but not enough wide angle pictures.
  • Jamie HallJamie Hall Member Posts: 9,326
    tfahlberg said:

    The main on the right is about 20' long before it disappears into a wall that I cannot penetrate. I looked everywhere that I could and did not find a vent for that main. Do I add a fourth Gorton to the left main to compensate?

    No! The idea of a vent at the end of a main is to get the air out of that main! Adding one to the other main will make any imbalance worse, if it does anything at all.

    Can you figure out where that main goes after it disappears into the fifth dimension? Is there a handy riser, perhaps, which is at the end of it? Or even a radiator feed? If so, though it's not the best possible arrangement, you can put a main vent -- or two or three -- on that instead. It must go somewhere...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • tfahlbergtfahlberg Member Posts: 20
    edited February 2018
    Thanks again for sticking with me guys. I should start by saying that I think that things have improved a bit after back-flushing the return trap. The boiler just now ran for about 45 minutes and only lost about 1/2" in the glass. I think that's 2-3 gals which is not good but it's better than before.

    jughne, I can't tell for sure about the slope of the mains. I always assumed they were level, but I stared at them for a couple minutes, and it seems like the left one slopes down a smidge from the boiler and the right one slopes up a bit.

    Speaking of the right main... Jamie, I understand. I won't add extra vents to the left side to compensate for the right.

    So I traced the right main to the end, where 3 pipes come off within inches of each other. I think they are all 2.5" (OD). The first is capped:

    The second rises; it probably goes to a single pipe rad on the second floor. (That rad heats up very fast.) The third pipe is just the reduced main; it goes laterally to a single pipe hookup (with no rad) on the first floor. After that, there is no more main.

    Could we put a vent where the cap is? It's before the rads so I'm not sure that's appropriate. Otherwise, Jamie, what about your idea to put a big vent on that bathroom rad?
  • Jamie HallJamie Hall Member Posts: 9,326
    What do you suppose those that capped pipe was? Probably never know. But -- if it really is hooked up to the main at the end, it would be a dandy place for a main vent. Or two or three.. It doesn't have to be before the radiators -- just very close. The radiator vents can probably handle what's left.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • JUGHNEJUGHNE Member Posts: 5,120
    Your picture of the steam main below the suspended ceiling with the window AC? in the wall behind the boiler to the left or the right of that picture?
  • tfahlbergtfahlberg Member Posts: 20
    To the right. That room is where the main starts sloping back down.
  • tfahlbergtfahlberg Member Posts: 20
    Still haven't been able to do the overnight leak test. It's been too cold to shut down the boiler for that long. But I did get more venting:

    NBC, I think the Big Mouth is equivalent to 2 Gorton #2. Since I need the equivalent of 3 Gortons, should I add a Gorton on an antler, or add another Big Mouth? They're the same price but the Big Mouth seems like a lot more for the money.

    In case anyone is wondering, I just picked up the phone and ordered the Big Mouth from the factory here in Massachusetts and got it the next day.
  • SkepticeltSkepticelt Member Posts: 8
    When you do the boiler water pressure test, slide a clean piece of cardboard under the entire boiler. leave the test on overnight. If you can isolate it, put a bit of pressure on the boiler. Pull the cardboard from underneath the boiler in the am and look and see if it has wet spots. That in my opinion would be better than trying to gauge if there is water in the exhaust. Beware you do not have other things that are dripping on the floor like a backflow preventer, they might give you a leak indication from the boiler when there is none. The pattern of the leak on the cardboard has its own tale to tell. If it comes out totally dry thats a good indicator that it is not the boiler. However not totally foolproof as the cast iron boiler could be leaking only when it gets hot.
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