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Large Boiler Leak When Steaming and Not Steaming

I am trying to identify the source of a very large leak in my boiler (i.e., my boiler has used approximately 600g of water in one year). The leak is very heavy during high season but also continues over the summertime when the boiler is not making steam and is just heating water (i.e., still used 21g of water from June 1 to September 15 this year during which time the steam system never ran).

The house was built in 1934 and much of the original system is intact, including main and dry/wet returns. It is a single pipe steam system with an oil-fired Burnham MST629 boiler that also feeds the hot water heater. The system also provides hot water to a baseboard system in an add-on to the house. There are 15 radiators connected to the system, a mix of convectors and sun-rads.

I’ve worked on several occasions with a reputable steam specialist that I found through HH who works in the area (I live in lower Westchester County, NY), but still have not identified the source of this massive leak. I suspect from having read several similar threads on HH that the culprit may be the approx. 1ft of buried wet return line (see attached photos). I am seeking advice to hopefully prevent me from having my new-ish (c. 10 yr.) boiler fail mid-winter. Any thoughts would be much appreciated.

What I’ve Tried
  1. Ran boiler to look for white smoke in the chimney. There was some, but my plumber indicated it was not bad enough to suggest a cracked boiler.
  2. Flooded boiler up to the header, no water came pouring out.
  3. Pressure test – Plumber plugged all the radiators and hooked up a compressor to pressure test the system. Pressure dropped slightly but not precipitously, and any loose valves or packing nuts were tightened.
  4. Plumber checked system piping in crawl space along with steam main vents. Did not find signs of piping or vents leaking on steam piping.
  5. Checked radiator vents and valves on all 15 radiators. Tightened all valves and packing nuts, nothing obviously loose or signs of water leakage.
  6. Reduced Aquastat from 190⁰F to 170⁰F (I did this over the summer when my plumber thought I might be losing water through excess evaporation while heating hot water).
What have I Not Tried?
  1. Replace the one buried wet return line. My plumber said that if there were a leak, water would be pouring out of the wall on one side or the other, which I don’t see. However, the openings on both sides sit above a French drain, so the water could be leaking out and getting picked up/drained off without me seeing it and/or could be getting drained off into the ground without leaking out into the wall. The pipe on both sides looks old and corroded/rusted.
Questions
  1. If there is a leak in the buried wet return line, would that cause the water level in the boiler to drop even when the steam system is not in use?
  2. Anything else I should try before replacing the buried wet return pipe?
  3. If I do replace the buried wet return line, any downside to not going through the wall and instead going around the short wall to keep it all exposed? (See pictures). Do I just adjust the pitch to account for the additional length of pipe? It would probably add another 8-10ft.
Boiler Water Readings:
Date Reading
01/10/2021 565
01/17/2021 568
11/12/2021 122 (counter turned over)
01/14/2022 338
01/22/2022 366
02/28/2022 449
03/14/2022 480
03/30/2022 511
04/18/2022 541
05/04/2022 557
05/11/2022 569
06/01/2022 599
06/26/2022 618
09/15/2022 620
09/19/2022 620 (Reduced Aquastat 190⁰F to 170⁰F)
09/24/2022 624
11/08/2022 714
11/14/2022 721







Comments

  • mattmia2
    mattmia2 Member Posts: 6,670
    Where does that return that goes through the wall go? It looks like it is just capped off and abandoned(or are there 2 pipe there that are concealed?)

    If you let the boiler sit without running it for several hours to a day or 2, does the water level in the sight glass go down? If you can see the level go down, you can confirm that the leak is in the return by lowering the level below the elbow in the hartford loop. If the leak is in the return the level won't fall.

    Is that wall block? If it is block it could easily be leaking in to the core and in to the ground. Even if it is concrete it could be running through a crack in to the ground.

    You can re-route the pipe, you just need to make sure if there is anything connecting to it under the water line that it stays under the water line.
  • Aprodromos
    Aprodromos Member Posts: 8
    Thanks for the feedback.

    Going to address your questions in-line:

    Where does that return that goes through the wall go? It looks like it is just capped off and abandoned(or are there 2 pipe there that are concealed?)
    The wet return enters the wall right there behind the freezer, goes through that 1ft thick wall, then comes out right behind the water heater. It's hard to get a good picture back there, but I think the part that looks like it's abandoned is actually a T where one side is capped and the other side continues into the corner behind the water heater then turns and follows the wall where it meets up behind the radiator with the other wet return line from the other branch.

    If you let the boiler sit without running it for several hours to a day or 2, does the water level in the sight glass go down? If you can see the level go down, you can confirm that the leak is in the return by lowering the level below the elbow in the hartford loop. If the leak is in the return the level won't fall.
    I'll try that, but I think I'll have to disable the water feeder, no?

    Is that wall block? If it is block it could easily be leaking in to the core and in to the ground. Even if it is concrete it could be running through a crack in to the ground.
    I'm not sure if it's wall block. A lot of the foundation is made up of a terra cotta like brick, so it could just be that and painted over. If it is, I agree that would make leakage and drainage in the wall easy.


    You can re-route the pipe, you just need to make sure if there is anything connecting to it under the water line that it stays under the water line.

    Noted. As I noted above, it does connect back up with the other section of wet return from the other branches, which I think I can just leave where they are.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,658
    Try what @mattmia2 suggested. Shut the boiler off mark the water level and disable the feeder and see if it leaks
  • Aprodromos
    Aprodromos Member Posts: 8
    So I tried this yesterday. I shut off the boiler about 730AM. At 830AM, I added some water to get it about 2/3-3/4 up the sight glass, marked the water line and then let it sit until 1230-1245 PM. When I checked back after 4 hours, no movement in the water line. I wasn't totally sure if it mattered whether the water was above the HL elbow or not, so I added more water to get it up to the top of the sight glass, which was definitely above the level of the elbow. That was 12:45. I let it sit until 530 PM, and checked back in. Water still had not dropped.

    My questions/observations:
    1. I took a video of the water in the sight glass, which has for a long time been very dirty once the boiler kicks on (dark brown, and the water level moves a lot). While I was watching it, I could see water/crud/cruddy water actually dropping in from the top of the sight glass. I've read many times on here that this condition is caused by oil in the boiler water, which can send water surging into your risers and create wet steam.
    2. Many of my radiators (but especially the ones upstairs) gurgle/kettle, but there is no water hammer (I resolved any sagging pipes with the plumber).
    3. Is it conceivable that I am losing that much water (600 gallons/year) to wet steam being released from my radiators? I don't have obvious water pooling at the radiators, but there is some corrosion/markings on some radiator vents that suggests some water comes out. It would not explain why my boiler used 20 gallons over the summer while the system was not steaming, but it could account for some.
    4. I have in the past tried to clean the sight glass and noticed that it is cracked/sheared off partially, but still fits into the spot just fine. Could this be a source of water leakage? Besides buying a new glass, are there any tips for replacing that I should be aware of (e.g., buy all new gaskets, etc.)?
    5. To deal with the dirty boiler water, is it better to skim, to Squick or to wand the boiler?
    6. This boiler is 12 years old, but I suspect it may have its life shortened significantly by all this water in-take. The house is 88 years old, and I believe the wet returns are original or at least very old. Is it worth replacing the wet returns preemptively to see if it improves water quality in the current boiler (along with a thorough cleaning), even if I think the boiler is perhaps not long for this world (at which point, I would probably replace the wet returns as part of the boiler change)? Any thoughts on how much it should cost to replace wet returns (it's two branches totally about 50-60ft of pipe, which other than 1ft that goes through a wall is all exposed)?
  • Jamie Hall
    Jamie Hall Member Posts: 19,960
    It doesn't explain the water loss during the summer (probably small leaks in one or more wet returns), but it is quite possible to lose 600 gallons in a season through various small leaks and leaky valves and poorly closing vents. Remember that one drop per minute leakage is a quart per day. And one drop per minute is a very slow leak -- you'd never see it on anything warm.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • random12345
    random12345 Member Posts: 293
    Did you check the floor for wetness underneath the union joints between the radiator valves and the radiators? You could install new vents on the rads if the ones you have now are old. Try Maid O Mist 0220-5L. Cheap and helps with balancing the system. Do you have a skim port? It might never have been skimmed. I believe it's tapping J in the manual:


  • Aprodromos
    Aprodromos Member Posts: 8
    Thanks. I checked all the inlet valves on the radiators with my plumber last time he was here and everything was tightened up. Every radiator vent in the house is less than 2 years old as I've been obsessively switching them out since I bought the house in Feb 2020 trying to get the system balanced (to no avail).

    The boiler does have a skim port and I was looking at that same diagram in the manual last night. The skim port has a nipple with a valve and even hose bib on the end of it, so I think it's set up for skimming. I've honestly just never skimmed a boiler before (first time homeowner, didn't even know what steam heating was when I bought the house), so I've been reluctant to try. Is there a particular set of steps to follow to skim (I presume someone on here has posted this before)?
  • 109A_5
    109A_5 Member Posts: 449
    Hello @Aprodromos,
    Many of those automatic water feeders have an orifice and the electronics just measures the time the valve is commanded open, so it is a calculated water volume not actually metered like a municipal utility water meter. Could the water flow through the automatic water feeder be restricted significantly so the readings are extremely erroneous ?

    so I added more water to get it up to the top of the sight glass

    How did you do this fill, a manual bypass fill valve or an activation switch on the automatic water feeder ?

    Maybe you don't have the actual water loss your automatic water feeder claims you do.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    Long Beach Ed
  • Aprodromos
    Aprodromos Member Posts: 8
    109A_5 said:

    Hello @Aprodromos,
    Many of those automatic water feeders have an orifice and the electronics just measures the time the valve is commanded open, so it is a calculated water volume not actually metered like a municipal utility water meter. Could the water flow through the automatic water feeder be restricted significantly so the readings are extremely erroneous ?

    so I added more water to get it up to the top of the sight glass

    How did you do this fill, a manual bypass fill valve or an activation switch on the automatic water feeder ?

    Maybe you don't have the actual water loss your automatic water feeder claims you do.

    @109A_5 - When I add water to the boiler for these purposes, I am using the manual feed valve not the little switch on the feeder.

    It's an interesting idea as to whether the AWF is working properly or over-stating the amount of water it is in fact feeding. Though I don't know how I would validate that.
  • Kickstand55
    Kickstand55 Member Posts: 51
    Frist: There's a lot of what if's and not quite sures with your diagnosis. Not trying to criticize but help.
    I love digging into a problem and finding a solution as many of us here do. It's what we do.
    Narrowing down and focusing on other potential issues may help. This requires breaking down each potential leak and doing a study/diagnosis.
    Is it your whole house water meter recording many gallons used? If not, how did you actually arrive at your figures? FYI: You can put a gallon water meter on the "boiler feed line to record it's own use".
    Second: If you have any old wet returns, just replace them no matter what. Cheap twice the price. They get slow returning condensate back to the boiler, (maybe this is part of the issue). I've seen some totally plugged and others almost closed off to the size of a pencil. Sometimes I've heard gurgling in radiators as a result of this as they can't give off condensate. Provide drains and wash out ports where possible to flush out and add pH correcting chemicals. Ferrous piping likes around 7 to 8.5 pH to combat corrosion. Also, has your boiler water been tested for minerals, chlorides and pH? Check the boiler mfg's. spec. on this first. It should/may be in the install manual that almost nobody ever reads. Grab a hot cup of coffee and have a good read. You'll be an expert in no time!
    Third: Oh yeah! Your domestic hot water expansion tank looks like it may need to be replaced. A rust spot is showing at the top fitting. Check to see it the tank feels heavy. If it is, it's waterlogged due to an internal bladder leak. When replacing that, you may only need an ST-5, 2 gallon tank for your application if your water tank is 40 to 45 gallons. Also be sure to provide a support to the beams overhead with a split ring hanger, 3/8" threaded rod and a beam hanger. Have a lead free 3/4" IPS ball valve with a waste port and a short lead free brass nipple installed between the tank and fitting. This makes for quick easy replacement. Too much weight and an unfortunate circumstance could break the fittings holding the tank.
    We're here to help as the tile indicates!
    Let us know what you find. We love to hear results.
    Dave
  • random12345
    random12345 Member Posts: 293
    edited November 18
    I'm not a pro, fyi, but skimming is pretty easy. This is the way I do it: Adjust your thermostat so the boiler turns on and fires until the water starts boiling. Then turn the thermostat off. Wait a while for the water line to settle. Get a bucket that won't melt from the hot water and place it under the skim port. Open the skim valve and let water drain out until it stops. Gently open the manual feed valve and set it so a pencil-thin stream is coming out of the skim port. Too little and there won't be enough current to get the oil slicks to slide out, but too much and I think the turbulence may cause some of the oil to remain pooled in the corners of the water surface. If it needed to be skimmed, the water will probably look oily/black. Just leave it like that for a while, maybe half hour or more. Then turn off the manual feed valve. Let the remaining water drip out of the skim port. Open the boiler drain valve to bring the water line back down to normal. Repeat every few days until the water only looks brown/rusty.
  • pedmec
    pedmec Member Posts: 664
    kind of curious how you pressure tested the system. Did you disconnect the radiator valves and cap the feeds. Remove the main vents.

    I definitely think you have a leak in the underground but it should have showed up in your pressure test. the water line in your boiler at the sight glass is not going to show you the leak because the hartford loop is too high. from the pictures its at the very top of the tankless coil. The top of the tee for the hartford loop should not be more than 1" or 2" above the bottom of the sight glass. Which would be about 2" below the normal water line. If it was at the correct location the you would see the water line dropping because it would have access to the return. but being so high the boiler is acting as a trap when you fill it up higher

    i'm surprised that you don't have banging and more trouble spots heating. you are getting steam in the return piping because the loop is so high. maybe the steam is leaking out of the underground return.
  • Aprodromos
    Aprodromos Member Posts: 8

    I'm not a pro, fyi, but skimming is pretty easy. This is the way I do it: Adjust your thermostat so the boiler turns on and fires until the water starts boiling. Then turn the thermostat off. Wait a while for the water line to settle. Get a bucket that won't melt from the hot water and place it under the skim port. Open the skim valve and let water drain out until it stops. Gently open the manual feed valve and set it so a pencil-thin stream is coming out of the skim port. Too little and there won't be enough current to get the oil slicks to slide out, but too much and I think the turbulence may cause some of the oil to remain pooled in the corners of the water surface. If it needed to be skimmed, the water will probably look oily/black. Just leave it like that for a while, maybe half hour or more. Then turn off the manual feed valve. Let the remaining water drip out of the skim port. Open the boiler drain valve to bring the water line back down to normal. Repeat every few days until the water only looks brown/rusty.

    So i followed these instructions and never got more than a relatively-steady droplets from the skim valve. I kept turning up the water thinking the flow was just too slow for the water to come up, but then water starting pouring out of two of my main vents. What did I forget to do?
  • Aprodromos
    Aprodromos Member Posts: 8
    pedmec said:

    kind of curious how you pressure tested the system. Did you disconnect the radiator valves and cap the feeds. Remove the main vents.

    I definitely think you have a leak in the underground but it should have showed up in your pressure test. the water line in your boiler at the sight glass is not going to show you the leak because the hartford loop is too high. from the pictures its at the very top of the tankless coil. The top of the tee for the hartford loop should not be more than 1" or 2" above the bottom of the sight glass. Which would be about 2" below the normal water line. If it was at the correct location the you would see the water line dropping because it would have access to the return. but being so high the boiler is acting as a trap when you fill it up higher

    i'm surprised that you don't have banging and more trouble spots heating. you are getting steam in the return piping because the loop is so high. maybe the steam is leaking out of the underground return.

    For the pressure test (my plumber did this, not me), he removed all the main vents and radiator vents and capped them off/plugged them. Then he hooked up an air compressor to the system and pressurized it, watching to see how quickly the pressure would drop. It dropped a little bit but not much.

    I did have a similar concern about the Hartford loop when I tried the leak test on the wet return. I at first set the water level in the sight glass about mid-way, it didn't drop, but then I added more water to put it right at the top of the sight glass, which was definitely above the HL elbow, and the water still didn't drop.

    I don't have banging in the radiators or in the pipes, but I definitely have some radiators that have trouble heating up (like as long as 20 minutes from turning on the boiler before they get heat). I've been trying like crazy with changing our main and radiator vents to balance it to no avail. I thought it was just insufficient main venting, but on that main branch I have two Big Mouths on an antler, which seems like more than adequate, even for a very long run with 9 radiators on it.
  • Aprodromos
    Aprodromos Member Posts: 8

    Frist: There's a lot of what if's and not quite sures with your diagnosis. Not trying to criticize but help.
    I love digging into a problem and finding a solution as many of us here do. It's what we do.
    Narrowing down and focusing on other potential issues may help. This requires breaking down each potential leak and doing a study/diagnosis.
    Is it your whole house water meter recording many gallons used? If not, how did you actually arrive at your figures? FYI: You can put a gallon water meter on the "boiler feed line to record it's own use".
    Second: If you have any old wet returns, just replace them no matter what. Cheap twice the price. They get slow returning condensate back to the boiler, (maybe this is part of the issue). I've seen some totally plugged and others almost closed off to the size of a pencil. Sometimes I've heard gurgling in radiators as a result of this as they can't give off condensate. Provide drains and wash out ports where possible to flush out and add pH correcting chemicals. Ferrous piping likes around 7 to 8.5 pH to combat corrosion. Also, has your boiler water been tested for minerals, chlorides and pH? Check the boiler mfg's. spec. on this first. It should/may be in the install manual that almost nobody ever reads. Grab a hot cup of coffee and have a good read. You'll be an expert in no time!
    Third: Oh yeah! Your domestic hot water expansion tank looks like it may need to be replaced. A rust spot is showing at the top fitting. Check to see it the tank feels heavy. If it is, it's waterlogged due to an internal bladder leak. When replacing that, you may only need an ST-5, 2 gallon tank for your application if your water tank is 40 to 45 gallons. Also be sure to provide a support to the beams overhead with a split ring hanger, 3/8" threaded rod and a beam hanger. Have a lead free 3/4" IPS ball valve with a waste port and a short lead free brass nipple installed between the tank and fitting. This makes for quick easy replacement. Too much weight and an unfortunate circumstance could break the fittings holding the tank.
    We're here to help as the tile indicates!
    Let us know what you find. We love to hear results.
    Dave

    Thanks, Dave. That's all very helpful feedback.

    The water readings I included in the original post are the readings from the automatic water feeder.

    Yes, that was what I was contemplating (just replacing the wet returns entirely since I think they are original or at least very old. I've not tried to have them or the boiler tested for minerals or pH (that I'm aware of). My plumber installed the drains/wash out ports, but I don't know if he ever actually flushed the wet returns of any gunk. I'll ask him, but I'll probably just replace them rather than trying to flush an already-backed up system.

    On the hot water expansion tank, yes, my plumber did previously catch that it was heavy and waterlogged, but he just re-inflated the bladder and it seemed to resolve the issue (it isn't heavy now and that leak stain has stayed the same as it has always been, hasn't gotten worse). I'm not even a novice plumber, so I don't totally follow what you're proposing in terms of the supports and the waste port. Do you have a picture of what that's supposed to look like?
  • pedmec
    pedmec Member Posts: 664
    You need to fix that hartford loop. Its going to affect how well the system performs. Its going to allow steam in the returns and cause issues with condensate return and system balance.
  • 109A_5
    109A_5 Member Posts: 449
    edited November 19
    Hello @Aprodromos,

    Though I don't know how I would validate that.

    If your automatic water feeder has One Gallon resolution. Let the boiler cool off so you are not dumping a lot of cold water into a hot boiler. Lower the water level to the range where the automatic water feeder, LWCO system likes to keep the boiler water level at. Then with a bucket calibrated in Gallons drain out maybe at least 5 Gallons. I would expect an automatic water feeder that measures (or calculates) correctly to show it put 5 Gallons of water back in to restore the water to the normal water line level. If it shows significantly more you found your issue.
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System