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Why is this radiator making so much noise?

dbrown Member Posts: 8
Hello all!

Let me start by saying that this is my second winter in this house and I would consider myself fairly familiar with the basics of steam heating. I've read two of Dan's books and I'm also an engineer.

The system runs very well and is generally very quiet (the Riello burner however sounds like a Boeing 737 at full taxi!) with the exception of one radiator. It also just so happens to be the one next to my bed and wakes me up most mornings.

The noise that it makes is a relatively loud metallic banging every 4-8s pretty consistently until the radiator is fully warmed up (air vent is closed). The radiator is silent once the air vent closes. It certainly sounds like water hammer but I don't see how that can be happening.

I've attached a few photos so that you guys can verify but I believe the radiator is pitched enough (the valve is to the right in the photo). The valve is nearly new and is fully open. It's hard to get a good photo but there are no obstructions inside the radiator that I can see - I can see all the way to the last fin. I've also tried doubling and tripling the pitch of the radiator and it seems to have no effect.

I certainly appreciate any help or guidance you can offer!


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    How is your main venting?—NBC
  • Mark N
    Mark N Member Posts: 1,115
    edited January 2018
    The air vent is installed upside down. Also how is the slide switch set? Fully opened or fully closed. Venting a rad too fast can cause it to hammer.
  • Neild5
    Neild5 Member Posts: 167
    Have you tried raising the entire radiator? If it has settled enough and the supply runs horizontal under the floor that section of pipe may have just enough water to hammer. Using a long 2x and a block very slowly raise the radiator and shim all 4 feet and then re check the pitch. I had to do that and put a 1x under the whole radiator.
  • FinishGuy
    FinishGuy Member Posts: 31
    I had a gurgling spitter radiator in my bedroom as well.

    I agree with @Neild5, try raising the radiator up. After attending to the other radiators in my home; correcting their slope, installing new air valves, and fixing the corroded main vent, the bedroom radiator still water hammered when the heat came up in the morning. I could actually hear the water moving in the pipe.

    I used an old scissor jack to gently lift the radiator at the balance point. I also used a threaded support pole in the basement which I placed under the black iron 90 where the feed headed up vertically to the radiator. I did this so as to not stress the old pipes as I knew from measuring distances that the riser must change from vertical back to horizontal for about 3 feet under my bedroom floor before joining the bedroom radiator. It involved some back and forth from basement to bedroom as I slowly lifted the radiator. The threaded jack in the basement I pretty much just kept in tight contact with the 90, supporting rather than lifting. FYI, I live on the second floor of a 1916 two family house converted to condos.

    In the end, I lifted this radiator 3/4 of an inch in order to pitch the unseen pipe enough to deal with the water hammer. I cut an old piece of closet pole to make legs for the radiator, which I was able to easily measure whilst it was supported by the jack.

    It hasn’t made a peep since.
    1916 two-family, now condo. Top floor. 970 sq. ft. of ‘well ventilated’ space. One-pipe, parallel flow, gas fired steam heat. 27’ of 2” main (un-insulated) vented via Gorton #2. 27’ 1 1/2” dry return (un-insulated) vented by Dole #5. 7 HB Smith Princess 2 col. radiators (38” tall) & 1 ARCo 30s era thin-tube 6 x 8 sec. (32” tall) = total radiator EDR 244. Using Maid-o-Mist radiator vents, sized by calc. & 14 winters tinkering. 1980 HB Smith G210-S-5 rated output 120,000 btu, poor near boiler piping.
  • Gsmith
    Gsmith Member Posts: 433
    A couple of thoughts:
    1. you said the noise is only every 4 to 8 seconds, it may be expansion noises of radiator legs or feed pipe rubbing against the floor. Try putting pieces of plastic (cut up a plastic milk bottle) under each leg and/or where the feed pipe goes through the floor.
    2. As mentioned earlier the radiator vent is upside down, try turning it upright and if that doesn't work, then change it to a slower vent (I like the ventrite #1 adjustable vents or Hoffman 1A vent), those Heatimer varivents are almost always too rapid a vent for most radiators.
    3. Make sure the buildings steam main pipes are vented and if possible insulated.
  • dbrown
    dbrown Member Posts: 8
    Thank you all for the great comments! This forum is awesome.

    NBC: Main venting seems to be ok to me. I have two runs off the boiler, each around 80 feet that drop down to the return in a crawlspace. Each elbow has a heatimer varivent opened up all the way. I know these aren't really main vents but they seem to work ok. The first radiator gets steam within 5 minutes of a hot boiler start.

    Mark N: I am aware that I installed the vent upside down. In fact I did this on purpose because I think the sticker on the "top" is ugly. I have 16 radiators in the house and they all have this same type of vent installed upside down and I have never once seen water come out so I think these can be installed upside down with no ill effect. Here's a photo of how the slide is set - hard to tell but it's open maybe 10-15%.

    Neild5 and FinishGuy: This is the way I'm leaning as well. You can see in the fourth photo above that I already raised the radiator about 1/2". The feet had dug into the hardwood over the years and dropped about 1/4". I put a 1/4" oak shim under it to raise it to 1/2" but it might need more. Indeed there are horizontal runs in the riser from the basement. There's one in the crawlspace that's about 5 feet and one immediately below the floor below the radiator that's about 2 feet. FYI, my house is 1915 so may be very similar to your 1916 :)

    Gary: I think you make a good point but expansion is a different sound - more a wooden type popping sound rather than water hammer banging. Trust me, I get plenty of expansion noise also but it's so intermittent and rare that it doesn't bother my wife or I (she says it's comforting because it means the house is warming up). The mains are absolutely insulated - that was one of the first things I did after reading Dan's books. I put on 1.5" fiberglass from McMaster-Carr (spent a small fortune!)

    I'll try to close off the vent more and turn it upright and see how that goes. If it still makes noise, I'll try to raise all four legs more.

    Thank you all for the input.
  • dbrown
    dbrown Member Posts: 8

    I flipped the vent over (so the sticker is on top) and closed it off all the way. No change in the amount of noise.

    I lowered the main pipe about 3/4" where this radiator branches off to try to pitch the horizontal sections of riser. I've finally been able to achieve 1/2" per 10 feet of pitch in the main but the horizontal section of the riser still slopes downward. This is in the crawlspace and the offending radiator is on the second floor. Could this small section of downward sloped pipe be the cause?

    I think the only way to correct the pitch would be to raise the whole radiator about 3-4 inches (or cut/rethread the pipe). Has anyone else had to do something so drastic?
  • Mike Cascio
    Mike Cascio Member Posts: 143
    That vent is TOO fast. Perhaps the riser or runout is sized one size too small and the radiator vent with the rate of a main vent will cause way too much condensate.

    Also, what are your main vents like?

    My bet a slower vent will make this problem go away.
  • BobC
    BobC Member Posts: 5,479
    Any horizontal pipe that traps water can cause water hammer, it has to be raised to achieve positive slope back to the boiler. The only other choice is that pipe has to be dripped at it's lowest point to get rid of the standing water.

    3 or 4" would be a lot of settling. That radiator valve looks a lot newer than anything else and newer valves are often shorter than the old valves. Sometimes people add a coupler and a nipple to get that valve up higher.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Fred
    Fred Member Posts: 8,542
    I don't like that you " lowered the Main to give the run-out some pitch." That will ultimately lead to water being held in the main. The solution for run-outs that need more pitch is to either raise the radiator at the far end of the run or shorten the vertical pipe that goes up to the radiator. Don't lower a Main, unless it has the wrong pitch.
  • KC_Jones
    KC_Jones Member Posts: 5,742
    dbrown said:

    NBC: Main venting seems to be ok to me. I have two runs off the boiler, each around 80 feet that drop down to the return in a crawlspace. Each elbow has a heatimer varivent opened up all the way. I know these aren't really main vents but they seem to work ok. The first radiator gets steam within 5 minutes of a hot boiler start.

    Am I to understand that on an 80' main you have a single heattimer as a main vent? If so that isn't even close to enough main venting. I would suggest you should be able to heat both mains entirely in close to the time you are getting the steam to the first rad. I would suggest you need roughly 6-7 times the venting capacity you currently have. 3 Gorton #2 per main or 2 big mouths would probably do the trick.

    The goal is to get steam to the inlet of all rads in the house at about the same time.

    Also I would suggest you turn the vents upright. All that installation will accomplish it potentially filling the vent with water and it never closing. They are designed a certain way for a reason, IMHO not liking the sticker isn't really a valid reason for an improper install. See this link for a cutaway as to what can happen when installed upside down.


    In the end you will most likely get rid of all of them anyway as they are crazy aggressive and really aren't needed with proper main venting. Even on the lowest setting those vents are fairly aggressive. I have one rad in my house that would make occasional noise with a Gorton #4. I ended up replacing it with a Hoffman #1A vent on its absolute lowest setting and that took care of it. It's all about the details.

    As for the noise I would concur with all of the above suggestions.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • New England SteamWorks
    New England SteamWorks Member Posts: 1,520
    I think you might have more luck by being aggressive with your main venting, and far less so with your radiator venting.
    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
  • dbrown
    dbrown Member Posts: 8
    Fred: The main did actually have the wrong pitch. I'm shooting for 1" fall in 10' (steam and condensate are co-flow) and there were spots where the main leveled off. That was the principle reason for lowering the main. I thought maybe lowering the main would help the pitch on the feed to the radiator but it doesn't seem to have helped much.

    KC_Jones: How fast do you get steam to the end of your main(s)? When my boiler has run recently (say within a couple hours), the end of the main gets steam within 4-5 minutes. Is that too slow? Those Gorton #2 are huge! Each of my main vents is simply a 1/8" tapped hole in the end elbow which is why I put the varivent in (I thought it would be the highest flow you could get through 1/8".

    I disagree about installing the vents right-side up or up-side down. However, that said I am going to try a smaller Gorton vent on this particular radiator and see if I can quiet it down. The old vent was a "C" so maybe I'll try that again.

    Thanks for all the responses! I have some ordering to do.
  • dbrown
    dbrown Member Posts: 8
    Update:. Installed a Gorton #2 at the end of each main (wow those things are large!). Also tried a Gorton C and and Gorton 6 on the offending radiator.

    Result:. Still damn noisy. With the 6 on there, the noise took a lot longer to start but once it got going there was no change. Still banging every few seconds louder than any other radiator in the house.

    I'm almost to the point of just turning it off and having a slightly colder bedroom... Any other suggestions?
    EBEBRATT-Ed Member Posts: 15,633
    Make sure the radiator take off from the main is with a 45 deg elbow. From the 45 all pipe must pitch up hill to the radiator and the radiator must pitch toward the valve.

    Your either holding water (because of pitch) somewhere or your venting too fast=letting steam in faster than than your pipe size will allow. If the pipe and radiator are pitched properly then the only fix is slow the venting or install larger piping. Check the size of the pipe against the radiator edr

    Condensate runs back to the main on the bottom of the pipe steam comes in on the top. Too much velocity in the steam=fast venting or too small a pipe cause steam to make waves in the pipe and causes hammer
  • Jamie Hall
    Jamie Hall Member Posts: 23,452
    A noise such as you describe -- very regular, and continuing until the radiator is fully warm -- is far more likely to be expansion than water hammer. Expansion noises vary, and while some can be wooden sort of sounding as you describe, some can be rather sharp metallic tings, bongs, and so on. Letting the feet slide may help, unless the noise is from the radiator sections themselves adjusting as they heat up.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ImYoungxD
    ImYoungxD Member Posts: 130
    "...loud metallic banging" sounds like a water hammer to me. Expansion noises are not loud but low to medium noises. You may have a pipe sagging under the floor.
    You should try changing the vent to a smaller one like hoffman 40. One of my radiator had very loud hammers and had varivalve. I replaced it with hoffman 40 and it's more quieter but still hammers (lightly).
  • Shalom
    Shalom Member Posts: 165
    Be surprised how loud some of those expansion noises can get, We've got one rad that goes "KONK!" every now and then; once while heating, again while cooling. Keep meaning to shove some plastic down around the pipe, but I haven't gotten around to it yet.
  • rmulye
    rmulye Member Posts: 3
    may I ask what is the pressure your system is set?
  • Lance
    Lance Member Posts: 271
    The noise may not be created at the radiator, consider it might act like a speaker for the transmission of sound. I have found causes of noise to be at the opposite end from where I heard it.
    I only know I would check all aspects of the system below the floor from end to noisy end. I assume the radiator valve is not being throttled down, it has pitch. Also there are not any hidden pipes in the wall? Old wet return clogged or poor flow?
    Some spirit banging on the pipes cause their too hot? Enough input there is not to guess accurately I can. The force flows it does though out the system.
  • neilc
    neilc Member Posts: 2,709
    isn't there a half inch of water sitting in the rad where the rad bushes up from 1 1/4 to the 3/4 inch valve?
    or did read that wrong?
    known to beat dead horses
  • Fred
    Fred Member Posts: 8,542
    I don't know how large/small this radiator might be but a 3/4" pipe and/or valve isn't large enough to allow steam in and condensate out during a heating cycle, on a one pipe system.
  • Chris_L
    Chris_L Member Posts: 336
    Hmm. A 3/4 inch pipe and valve? That looks like 1 1/4 stamped on the valve in the original post. Where is the 3/4 inch coming from?
  • the_donut
    the_donut Member Posts: 374
    3/4” was in reference to someone raising a radiator to correct a sag in a runout under the floor. I had a radiator with a similar issue. Previous technicians labeled it as expansion noises. Issues was with runout pitched wrong direction below floor. Water was sitting in belly and being blown into radiator.

    We had to raise radiator almost an inch before noise would stop. Also had tenants upstairs shutting radiators off and opening them sending condensate shooting down the pipe.
  • Fred
    Fred Member Posts: 8,542
    edited February 2018
    @ChrisL , I think I may have confused this thread with the one from @condensationpoint . He is feeding a radiator with a 3/4" supply. :(
  • Jay Zebryk
    Jay Zebryk Member Posts: 16
    edited February 2018

    1) I have a box of dead Heat-Timers which have failed after short service.
    a) Stuck Open
    b) Stuck Closed
    c) Stuck Somewhere in-the-middle.
    An easy test is to remove when cold and blow into it compared to a brand-new one.

    2) Upside-down, water can surround the alcohol
    diaphram "insulating" it from steam and never close.

    3) Get a Gorton #D for your test kit to use as a control to test against.

    4) In venting your mains with the big Gorton's, did you make up an adapter for your 1/8" tapped holes?
    If so, you should be using a T with a 1/2" port instead.

    5) In your photos, the level reads "just-cracked".
    You might try slipping a checker under the vent side and see what happens.
    (Loosen your spud nut a bit to allow it to move without stress.)


    Jay Zebryk
  • neilc
    neilc Member Posts: 2,709
    I think I'm with @Fred
    I also seem to be commenting on the wrong thread about the 3/4
    disregard , , ,
    known to beat dead horses