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Gurgling Radiator

DTO Member Posts: 13
Hi all. First post.

I just bought a three-story 30s colonial in central NJ. It has a gas-fired 1-pipe steam system.

The radiator in the bedroom on the 2nd floor and the radiator in the office on the third floor are fed via a single riser. There is a wicked water hammer in the riser and in the 3rd floor radiator, and the 3rd floor radiator makes gurgling and wooshing sounds. The hammering and gurgling occur at the beginning of the cycle, and pretty much go away once the radiator heats up.

The riser is 1 1/4"  when it begins at the 2" main in the basement. At the 2nd floor radiator, there is a tee to the radiator valve for the bedroom radiator. From the tee, a 1" riser (the tee is 1 1/4"-1 1/4"-1") continues to the 3rd floor.

At the third floor,  the riser ends at a 90* elbow and a horizontal run of about 18" (behind the wall), then another elbow and a 8" horizontal where the 1" pipe comes out the wall to the valve for the office radiator.

Here is some history:

When we moved into the house, the water hammer was present in the 1" riser to the third floor and in the third floor radiator. I also noticed gurgling and wooshing sounds coming from the 3rd floor radiator.

I replaced several of the radiator valves in the house and lowered the cut-in pressure from 1.5 psi to .5 psi and the hammer quieted. I lowered the water level in the boiler a hair (from 2/3 to just above 1/2 when cold) and the hammer stopped.

Last weekend I insulated the main (it was uninsulated when we moved in) and replaced the small main vent ( I suspect it was stuck open) with a Hoff#75. These repairs did a great job balancing the temperature in the house and getting the radiators throughout the house to heat at the same time. However, the hammer returned, and the 3rd floor radiator is back to wooshing and gurgling with a fury.

This weekend I checked pitch on the 3rd floor radiator and horizontals. It was okay, but I was able to add another 1-2*  to the horizontals by cutting a notch in the drywall where the pipe exits the wall and putting the radiator up on a piece of 3/4 plywood.

I also disconnected the radiator and checked it (and the valve) for debris or corrosion and found none. I did drain a cup or so of water from the bottom of the radiator. (!!)

These efforts had no effect on the noises. The next cycle was somewhat subdued, but still noisy. The second cycle after the repairs was just as noisy as before.

Here are a few other possibly relevant facts:

- The 3rd floor office radiator is different (and larger) than most of the others in the house. It is much taller (maybe 36") than all of the other radiators above the first floor.

-The riser is not insulated.

-There is another riser that feeds radiators on both the 2nd and 3rd floors (pretty much the same setup as described above) and that branch operates quietly. The radiator on the third floor on that branch is the same smaller radiator that is found in all of the other bedrooms of the house (not like the large one in the office on the noisy branch).

-My wife and I sleep in 2nd floor bedroom with the noisy riser; I haven't slept for days, and she is about to kill me if I don't figure this out!!

Any ideas? ... other than moving to the other bedroom.

Thanks in advance.



  • Jamie Hall
    Jamie Hall Member Posts: 20,868
    A couple of thoughts

    more or less off the top of my head here...

    Venting.  Does that third floor radiator have a bigger or faster vent than some of the others?  Try slowing up the venting on that radiator  Perversely, that sometimes helps.

    In fact, in this situation it may help a lot: those pipe sizes sound to me to be possibly a little small: the riser will only take about 45 square feet, and the horizontal runout will only take 28 -- even pitched at a half inch per foot.  Slowing the venting may not cure the problem, but it might make it better...

    I'm sure someone else will have some ideas, too!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • DTO
    DTO Member Posts: 13

    Thanks for the response.

    The radiator has a varivent. Putting it on the "close" setting had no effect.
  • gerry gill
    gerry gill Member Posts: 3,054
    do the runout pipes

    have sufficient pitch? all of them? every linear foot of them? are the runout pipes large enough for the load on them?
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Gurgling

    I'd also check the steaming capacity of the boiler.  If the boiler is too big, it can fill the system with steam too quickly and have excessively high velocity that does not allow the water to drain back down the run outs. Increasing the venting increases the steam velocity, especially with an oversized boiler, which may be your problem.

    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • Bill_110
    Bill_110 Member Posts: 52
    gurgling radiator

    Just to clarify you say that the noise occurs after the system first starts up and then ceases when the piping warms up? How much of the 3rd floor radiator warms up at the end of a cycle, and how frequently does the boiler cycle on during the nite roughly?  I have  a similar problem myself, I haven't really figured it out. If your third floor office room isn't being used at nite I wonder if shutting off the valve to it during the nite might quiet things somewhat as a temporary measure?
  • Bill_110
    Bill_110 Member Posts: 52
    Steam velocity

    If your system has high velocity steam problems from something like improper near boiler piping, until you had this problem corrected would fast venting be a problem on the Mains as well as the radiators? I know I've seen recommendations on this site and in Dan's books for trying a slow venting approach on some radiatiors, but I also got the impression that you  couldn't have too much venting on the Mains, or would there be an exception to this last rule if the velocity of your steam was already too high? Thank you for your input. 
  • DTO
    DTO Member Posts: 13

    Thanks for all of the replies.

    Pitch was the first thing I considered. The pitch of the horizontals is good. Perhaps even too much (if that is possible). The riser is near vertical, with a slight lean toward the horizontal & radiator. The radiator is pitched about 2.5*.

    Not sure what the right answer is about venting.

    I replaced the old vent with a new varivent, and have tried open and closed. The noise is present in either case. If open, the noise seems to be more in the radiator rather than both radiator and riser. Also, when open the vent will spit.  If closed, the riser will tap-tap-tap, then louder banging as steam reaches the radiator.

    As for frequency of cycles, I have my thermostat set to 70* in the evening, then 66* at night, then 70* in the early AM just before we wake up (so the bathroom is warm for shower-time). Right now (it has been dropping only down to the 40s at night) the system has adequate heat from the evening to carry it through the night so that the first cycle is when the temp goes up to 70* in the early morning.

    Bill, last night I tried exactly that. For the first time since I increased the pitch on the radiator and horizontals, I turned off the radiator valve to try to mitigate the noise. When the steam reached the riser to the third floor, it let out a few faint taps (which probably wouldn't have woke me up, except that I was already awake waiting for the banging). I thought the temporary solution had worked until 5 or so mins later, when the banging from the third floor was so bad that I heard it in the shower. It sounded like it was coming from the horizontals or radiator upstairs. I opened the radiator valve and heard the steam wooshing and gurgling into the radiator, and the banging stopped.

    A question for the pipefitters: what would be the ideal way to plumb the horizontal on the third floor? The riser comes up through the bottom of the wall, so an elbow is necessary, at least to get it out of the wall. It comes up at a point in the wall at the middle of the room, which is why they added the 18" horizontal -- to get it closer to the corner.  Would it be better to use a 45* closer to the floor, then another 45* to the radiator (if this is even possible in the space) so there are no 90* bends. Right now there are 3 x 90* elbows from the riser to the radiator.

    Another question: is it possible the radiator is bad -- or maybe the wrong size for that location in the house?  Like I said in the initial post, when I disconnected it, a bunch of water came spilling out, and the system had been off for a while. I imagine if this pool of water is in the radiator when the steam hits it, the steam would condense in an instant.

    One more: Although the pressuretrol is set at .5-1.5 psi, I looked at the gauge this morning mid-cycle (just after the banging) and it was at 3psi. I'm guessing the p-trol is bad. Right? Would excessive pressure prevent the condensate on the third floor from being able to get back down past the steam? It has a Honeywell PA404 right now. Is there anything better than that to replace it with?
  • brian_44
    brian_44 Member Posts: 59
    edited November 2009
    Hey Damon

    I'm sure you'll get lots of good ideas here. This site along w/ Dan Holohan's books have helped me tremendously.

    The water you mention in your big upstairs radiator may mean the valve is bad/clogged (This could happen if you suddenly pitch the radiator and all the years worth of crud clogs up the valve) or you have a sag in the middle of the radiator (which was the issue with mine...as I had a hammering/gurgling issue with an oversized radiator as well which sounds very similar.)

    I'm sure someone will ask you to post pictures. Others here will benefit greatly from being able to "see" the radiator and any pipes you've described.

    If there is an area you can put shims under the middle of the radiator to help correct any sag in the middle, that might help as it did with mine.

    It is possible for the radiator to be pitched TOO much. I usually get a level and just make sure there is a slight pitch on mine...nothing radical.

    I'm not a pro...just some things I did to remedy a similar issue.


    Oh...one more thing. That pressure is WAY too high on your boiler. You shouldn't even see the PSI read on that gauge, so you might have a clogged pigtail, but I'll let a pro here walk you through what to do on that...
  • DTO
    DTO Member Posts: 13

    Hmm. Clogged pigtail. I hadn't thought of that. I will check.
  • DTO
    DTO Member Posts: 13
    Clog in riser?

    The valve looked clear. I checked when I had the radiator off. Do you think it is possible that crud made its way into the horizontal run or riser, which may cause a problem since they are on the small side. Can anyone suggest a way to clear or flush the riser? Garden hose to the third floor comes to mind. Is this crazy?
  • brian_44
    brian_44 Member Posts: 59

    ...actually now that I think about it, if the pigtail were clogged, you'd probably NOT get a reading on the gauge...but it's easy to check anyway.  Sorry to run you in any circles.
    STEAM DOCTOR Member Posts: 1,622
    gorton #4

    try a gorton #4. the varivalve in the closed position vents about 3-4 times as fast as the gorton#4.i know it sounds odd but its true. take a look in Gerry Gills venting capacity chart available on this site. the varis are also more prone to spitting then other air vents good luck
  • AlexR
    AlexR Member Posts: 61
    don't trust the gauge

    If you read 3psi on a 0-30psi gauge, don't necessarily trust it.  Mine was doing the same thing.  I just installed a 0-3psi gauge and it reads 1.6psi when the pressuretrol (L404F) shuts off and then the reading falls until the pressuretrol cuts in.  The 0-30 gauge never moves from 3psi once the boiler is hot, so it's clearly broken (or at least useless at pressures that low).  Ideally you'd install a low pressure gauge so you can see what's really going on, though that may be more work than you're up for to fix a gurgling radiator.
  • brian_44
    brian_44 Member Posts: 59
    Could be...

    With what you're describing, a lot of things are possible. You might simply need to flush out the radiator to get all the crud out of it also.  If I were you, I would probably contact a pro to come check it out and make recommendations rather than live with the problem. It would be well worth it...  
  • gerry gill
    gerry gill Member Posts: 3,054
    since you got water spilling

    out at you when you disconnected the radiator after the boiler had been off for a while i would believe thats the problem..why doesn't the water drain back on its own? find that answer.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • DTO
    DTO Member Posts: 13
    Back to basics.

    Okay, here's an update. I'm going in a few directions here, but making progress.

    I checked the pressure gauge (which is 1-30, btw) when the boiler was stone-cold and it was reading 2.5 psi. I removed it, and it was still reading 2.5. I banged it on the bench a few times -- still 2.5. I'll be replacing it.

    The tip about the clogged pigtail was spot-on. When I took the gauge off, I could see that the pigtail was clogged solid. It took a good 1/2 hour with the torch, but it is clear now. Pressuretrol seems to be working now, although I can't tell how accurately until I get my new gauge, which should be in the next day or so. In any event, the general hissing and spitting in the house (which wasn't too bad to begin with) has quieted. Progress.

    As for the cranky radiator, I went up there over the weekend while it was having a banging fit (I was in a bit of a fit myself, since I am getting frustrated with this thing), and I heard it gurgling and churning away. I pulled a piece of closet rod (prob 2" round) from where I had just installed one in the office and jammed it under the back of the radiator. There was a big wooshing surge from within the radiator, one loug clang, and the banging stopped. The radiator is now pitched about 10*. It looks ridiculous, but it is relatively quiet. It no longer bangs, but I can still hear the steam surging inside the radiator and riser. My guess is that the problem is in the radiator. If I can find one nearby, I will swap it out. Craigslist, here I come!

    The vent on the problem radiator still hisses more than the others in the house (hissing from the others is pretty much nil, now). Actually, you can hear the vent "breathing" while the radiator is getting hot. It intermittently sucks and blows air. I still have the varivent on the radiator, but I have an extra Hoffman 1A in the basement that I will try when I get home today. I don't have Gerry G's vent chart, so this will be trial-error to see how it affects balance. Right now, things are pretty good as far as balance is concerned. Pretty much all of the radiators (including the 3rd floor office) are getting hot at the same time. Kitchen is the only one that is a bit slow (even with the varivent wide open), but it is last on the main and on the first floor (which heats pretty well from other radiators), so not a big deal.

    Thanks for all of the advice.
  • brian_44
    brian_44 Member Posts: 59
    edited November 2009
    Great to hear

    That you've made progress.  Glad about the pigtail too...I found myself second guessing it, but glad the suggestion was helpful.

    So you know (as I've mentioned before), I have a somewhat similar issue with a radiator in my home. The "heavy breathing" sound you hear reminds me of mine... With the proper pitch, I'm able to get by, but if the heat needs to rise several degrees mine start to gurgle also. 

    Before replacing the rad, (and I don't remember if you did this already) try flushing it out. That may be all it needs (I'm going to do that w/ mine after the winter...but it's a 6 foot long BEAST).

    Glad to hear you've made progress though. Looks like you're on the right track...

    As far as the radiators heating up in the house together...make sure your main vents are adequate on your mains. I had one that was basically blocked. Didn't even realize it. I put in a Gorton #2 and it cut the time to get heat to my radiators by at least 15 minutes...and they all get hot about the same time. That's probably one of the most overlooked things in a steam heating system for most homeowners I'd guess...You can see a picture of it on an "antler" on the top of the picture.
  • DTO
    DTO Member Posts: 13
    Main Vents

    Brian, I though about flushing the radiator, but not really sure what to use. I'm a bit paranoid about using something that could contaminate the system.

    The system is split into two branches.

    The first is the "main branch, which feeds most of the house. I just replaced the small and defective (paint, rust, blech!) vent on that branch with a shiny new Hoffman #75. 

    The sub-branch feeds only three radiators; two on 1st floor and one on 2nd.  There is no vent on this branch. I will be installing one in the spring. For now I have all the vents on these rads wide open, and they heat pretty much evenly with the rest of the house.

    Quick question about the placement of main vent. Everything I've read recommends placement of the main vent about 16" from the end of the main (to prevent flooding, I think). Right now, the main vent is on a tee right at the end of the main, and the vent HAS flooded in the past (although not since I cleaned the pigtail and got the pressure down). Is it worthwhile to move it from the end?
  • DTO
    DTO Member Posts: 13
    More mains

    Brian, I just looked more closely at the pic of your main vent, and I see that yours is branched off the end of the main on a short elbow. Does your main ever spit water? If this setup works just as well, I might try it instead of breaking into the main to move the vent further upstream.
  • brian_44
    brian_44 Member Posts: 59
    edited November 2009
    My Main Vent

    My main vent was in that place since we moved in, and I thought I'd give it a shot with the vent where it already is. It is ideal to have it some distance from the return line heading down to the boiler, but since it does not spit water (which is one of the reasons the antler helps...the water would have to do a complete u-turn or even a 90 degree left, then up in order to shoot out) I have not moved it. If you have a vent in the same place already, you can try it first and see what happens as well.

    Also (just noticed your prior post), type in "flush radiator" in the search section here and you'll see some helpful hints on flushing a radiator. You'll need to remove it and take it outside (which is why I'm waiting to do mine after the winter).
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