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help - hammer in radiator

JH_2 Member Posts: 57

I've been making good progress on tweaking my single pipe system with your help, but now Im stumped.  One of the two radiators on my second floor is hammering.  I am positive that the hammer is in the radiator itself - the noise is very loud at the radiator, and we hear it somewhat in the vertical riser on the first floor, but barely at all in the basement.

The radiator is a 8 section 3 column steam type of 40 EDR, on a 1 1/4 riser.  The run-out to the riser in the basement is pitched, but not the 1" per foot recommended, maybe 1" per 20... But yet there is no hammer in the basement.  I did block up the radiator to pitch it toward the valve a bit, no improvement (also had to block it up level level side-side... very old house).  I also opened up the valve and checked that it is fully open, no improvement.   I changed the vent and tried a very slow vent - no improvement.

A couple of things I noticed that maybe the cause?

- The valve on this radiator was replaced. maybe the new one isnt big enough?

- The radiator does seem to have a very slight sag in the middle (maybe 1/8") and when I had it off I could see that a lot of water pools in the bottom of the sections.

What should I try next?  Should I pitch it even more??




  • Steamhead
    Steamhead Member Posts: 16,454
    First thing I'd do

    is take the radiator off the valve and see if anything is caught in either the valve or the radiator. This isn't usual but it still can happen.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • JH_2
    JH_2 Member Posts: 57

    I had it apart once and it didn't appear blocked, but Ill try again. more news tomorrow....
  • dennis8
    dennis8 Member Posts: 15
    Had the same problem

    I had the same problem on a third floor radiator.  Hammering seemed to come from 1st third of raditor(from valve side).  I read on this site that someone suggested lifting the valve side slightly.  Then correct the pitch, so it is higher on the vent side.  This person suggestred using a 2x4 a lever with a small piece of 2x4 under it.  That really saves your back.  This worked for me.  Good luck
  • SBoston
    SBoston Member Posts: 61
    Same problem with my second floor radiator

    Just last week I had the some trouble with my second floor radiator. The trick to resolving this problem was three fold.

    1) Insulation - the lack of insulation on the riser was causing condensation to shoot back up into the radiator (also caused a swooshing sound)

    2) Slower vent - I removed the adjustable vent and installed a slow venting Gordon… also eliminated the TING sound of the value opening and closing (Bonus)

    3) Very fine adjustments - I fine tuned the angel with small wood shims, I did a very little at a time.   

    The only thing I hear is the gentle sound of the metal expanding.
  • JH_2
    JH_2 Member Posts: 57
    edited October 2009

    Thanks for all the extra suggestions.

    I actually do have the riser insulated where it passes through the first floor (Did it so I could paint it to match the wall  and cut down excess heat).

    I did lift raise up both ends of the radiator (to get it level side-side) before pitching the vent end up.  Id say I lifted the valve 1/4" from what it was and pitched the other end 1/8-1/4 higher than that.

    I'm going to disconnect the radiator again tonight and check for obstructions.  I'll post photos.

    If that doesn't help then I'll pitch it up even more.
  • JH_2
    JH_2 Member Posts: 57
    no blockage

    I took the radiator off. I se a lot of scale but no blockage in the sections. valve looks clear.

    Not sure if you can see it well in the photos...

    So I put it back together and added another shim to pitch it up a bit more. Also turned the vent down a notch (H1A adjustable)  Lets see what happens the next time the heat cycles....
  • JH_2
    JH_2 Member Posts: 57
    No good

    So I tried pitching the radiator some more.  Now its about 1/2in high at the vent end. No good, it still hammers quite a lot at startup.

    One thought I had. Here is a photo of the original valve at the other radiator on that floor that was not replaced.  That other radiator doesn't hammer.   Is it possible the replacement valve is causing the problem?
  • Jamie Hall
    Jamie Hall Member Posts: 22,100

    If the replacement valve is either designed or installed in such a way that water can't drain completely -- really totally completely completely -- it's going to hammer.  Make sure that when the valve is open, the passages have at least the cross section area as the pipe, and that there are no obstructions to water flow (for example: is the seat design such that it can't trap any water?).  Not all valves are created equal (and it's no comment on either design or construction -- there are some very high quality angle globes available which simply aren't suited for one pipe steam).

    Once that's checked, make sure the valve is fully open -- but you knew that!

    And if it is still hammering, come on back and we'll all think some more!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Unknown
    edited October 2009

    You might want to back off on the pitch a bit - 1/2 inch is way too much!     5/16 inch would also be a bit on the high side. I use stacked quarters ($0.25) when i''m experimenting with slope and on a level floor 3 is usually the max.for a radiator that size.

    You didn't say when the water hammer was happening. Is it continuous or say just at the beginning of the heat cycle?  You might try slowing the venting. If the radiator is venting too fast, especially at the beginning of the heat cycle when the cold radiator is  condensing like crazy, a large volume of condensate (water) is being produced. Slower venting will slow down the water production. You might try choking the vent with a small ball valve and see if that makes any change.  I have attached a picture of the setup I use to test radiator vents. When the vent closes you get a spike in pressure. It also helps with timing the radiator.

    When I first saw your pictures I was a bit suspicious of the new radiator valve too. I've seen others that don't block the passage quite as much as this one does.  Do you have the old valve to compare it to? I'm not that experienced with different brands of radiator valves so can't say for sure if this might be a problem.

    - Rod
  • JH_2
    JH_2 Member Posts: 57
    Rod.. Jamie...

    I don't have the old valve, it was replaced before I bought the place - but I assume it was the same type as that white valve on the other radiator.  It definitely looks larger externally but I don't want to open it up if I don't have to. Moving the bad radiator without wrecking the floor  was a bear :(

    The pitch got to 1/2in because I keep raising it more and more in hopes of a fix.  OK, now Ill drop it back down to nearly level and start over - see what happens.

    I will also turn the vent down. Its a hoffman 1A, currently on #2, but I'll switch it to #1.  I also have a spare  ventrite #1 I could swap... those vent even slower I think.

    Appreciate all the ideas, I'll be working on it again tonight after I get the latest batch of firewood stacked.

    More new tomorrow..........
  • JH_2
    JH_2 Member Posts: 57
    Latest Update

    OK. So last night I took out 2 shims and dropped the pitch of this radiator down to only 1/8" high on the vent end.  I also turned the hoffman 1A vent down to the #1 setting.

    So far it seems better- not gone, but better.  I did hear a bang but only once or twice on a short heat cycle last night, and this morning it did not wake me up when the heat came on at 6am like it had been doing previously.  However with the mild weather the cycles have been too short to heat it beyond the first 1-2 sections so time will tell if the banging comes back on colder days with more/longer cycles.
  • Radiator

    Sounds like things are moving in the right direction. i thought I'd mention this as you said you might try changing vents. According to the venting chart, a Hoffman 1A at the #1 setting is a slower vent than a Ventrite #1 at the #2 setting (#1 is OFF).

    On the valve problem -  It occurred to me as a last resort if all else fails, maybe you could just replace the valve with an elbow. Nobody ever uses the valve anyway as they either have to be fully open or fully close and even fully closed they can cause problems.

    I'm not sure it one can really ever totally eliminate noise problems with a 1 pipe steam system. I've seen old advertisements for a 2 pipe steam system where they mentioned the benefit of how quiet it was. I had problems with my system for a while but was able to get the percussion section to stop playing and now just have the occasional "clink"

    - Rod
  • JH_2
    JH_2 Member Posts: 57
    Spoke too soon

    The last couple night have been mild. Seems that the rest of the radiators would warm and satisfy the thermostat before this radiator even started to heat.

    So I turned the vent up just a bit (to #2) and we had a colder night.  Bingo - hammer woke me up again.  It seems to start as soon as the radiator begins heating and continues for the first 10 minutes or so of the cycle.

    I know one pipe isn't always dead quiet - but out of 9 radiators in my house this is the only one that makes any noise at all - and of course its affecting the bedrooms... I'd just live with it if it were at the other end of the house.

    Any other ideas before I give up and just shut it off (I'd rather deal with short cycling than being woken up at night all winter)? Recommendations fora better shutoff valve to swap maybe?
  • JH_2
    JH_2 Member Posts: 57
    riser and runout

    If it prompts any ideas - here are photos of the riser  (whch passes throught the master BR) and the runout in the basement.

    In the basement photo, the runout to this riser is the one in the foreground. There is a ~3ft section thats pitched only very slightly, that then elbows into another 3ft section that pitches steeply down to a 45 into the main. 

    Note that I never hear any hammer in the basement... only the faintest echo if you listen to the pipe.  Its definately coming from the radiator itself.
  • Valve

    From your pictures there doesn't seem anything really out of place and since you seem to center the noise on the radiator that would seem a more likely area for concern.

    This may sound a bit nutty, but I just had a wild thought.   Why not open the radiator valve up (take off the top) and remove the check plate and the rubber gasket from the valve stem and see how it operates without them?

    - Rod
  • JH_2
    JH_2 Member Posts: 57
    no luck

    I got the valve apart... but you cant remove the check plate without destroying it.  The rubber gasket can be removed, but the plate itself floats on the end of the stem. It looks like they pressed it together at the factory - kinda like a captive ball joint.

    The valve itself is marked "Legend Valve Co - Taiwan"  Is there a better brand of valves out there that might be less obstructive?
  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    Can you

    just thread the bonnet of the valve back on, without the stem and all, and seal the hole temporarily with something?  There isn't that much pressure, after all.

    Legend valves, Taiwan?  Ah... no offence to our Chinese friends, nor to the big box stores, but I'd be surprised if a trip to a good plumbing supply store didn't come up with a better valve...  Of course, I've seen some rather strange threaded fittings at plumbing supply stores lately, come to think of it...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JH_2
    JH_2 Member Posts: 57

    I'm becoming more convinced the valve is the culprit.

    I checked their catalog, the local pluming supply outlet where I get stuff (F Webb) carries these "Legend" valves.  That's probably where the P.O's plumber got it.  HD/Lowes has  cheaper junk.

    I checked around and it looks like Pex has "Matco-Norca"  and State Supply carries a few brands including Hammond and Mepco. Any of these any better than this Legend brand valve I have?
  • valve

    Jamie's idea has merit.. If you can take the handle off and remove the stem assembly you probably could plug the stem hole with a short bolt of the same size as the stem. You also might call Webb (They are pretty big and  I can't imagine that they just carry one brand of valve)  and ask them what they have in a steam valve besides Legend.

     I'm afraid I can't help you much with valve brands as I haven't replaced that many and quite frankly have never thought of examining  their inside clearances.
  • JH_2
    JH_2 Member Posts: 57
    edited November 2009
    re: valve

    Ok I scrounged around the basement and found a 1/4-20 bolt and a couple big rubber washers that should do the trick. I took out the valve stem and plugged the hole - lets see what happens next time the heat comes on.
  • JH_2
    JH_2 Member Posts: 57
    Didnt work

    Gutting the valve didn't work.  Still hammering away.  I sat next to it as the heat came up and basically, as soon as the valve is warm and the first section just barely starts warming, the hammering begins.  It sounds like its coming from the middle of the radiator.

    At this point I'm out of ideas. I re-read the chapter on hammer in lost art and I think we have tried everything. Slow vent, open valve, pitched radiator, mains are insulated, risers insulated,  proper main vents, low pressure, pipes not undersized, etc etc.  The only thing I can see wrong with the setup is that maybe the run-out in the basement needs more pitch... but yet I still don't hear anything down there.
  • juliachicago
    juliachicago Member Posts: 22
    Could it be the radiator

    Hello -

    I'm no expert at all, but I thought I'd throw in my two cents.

    I have had a similar problem recently. In my study, I had a radiator that banged (so so loud) when the heat came on, and my plumber and I tried everything (pitching changes, new vent, new valve, etc.). It got to the point where I was pretty sure there was some sag in the pipes in the floor and the only way to fix it would be to tear up floors to get to the pipes, which I can't afford to do). I asked my handyman to swap that radiator with an identically sized one in another room in the house, to see which one banged (to rule out pipe vs. radiator issue). The radiator that banged in one room banged identically in the other, and the previously silent one continued to be silent in its new room. I bought a used radiator to replace it ($125) and now there is silence. This drove me nuts for a while and I never really thought it was the radiator itself until I ruled everything else out.

    Just an idea

  • Bad Radiator

    Rats!  I'd have sworn it was the valve.  As Julie said, It must be the radiator and you did mention in your first post -"The radiator does seem to have a very slight sag in the middle (maybe

    1/8") and when I had it off I could see that a lot of water pools in

    the bottom of the sections." I guess this is causing steam collapse and hence water hammer.  Other than replacing the radiator I'm not sure just what you could do.  Possibly you could put some blocks under the center of the radiator to shore it up.

    When you had it at maximum slope, did it make a difference? This usually causes more problems than good though I'm just thinking of how you can get the pooled water out of the bottom of the radiator.
  • JH_2
    JH_2 Member Posts: 57

    So I checked the radiator again.  I thought there was some sag, but when I checked the top with a long straightedge I dont see any sag after all.  I also disconnected it again and only 2-3 tsp of water dripped out. So I dont know if pooling condensate is the issue.

    Looking inside I can see a pile of rust scale built up at the far end.  Looks like it was leaned away from the valve for years. but other than that it looks ok.  So I hooked it back up and tried one more thing - I swapped out the hoffman 1A vent for a vent rite #1.  I really really doubt this will do anthing but I cant figure what else to do. I cant see how the radiator could be bad if there isnt water pooling in it??  In any case I dont feel like breaking my back swapping it out unless there is no other option...

    fingers crossed.
  • Choke it?

    Hmm...sort of running out of options. Any chance the rust pile in the radiator is moving about? 

     I think I'd try choking the vent.  I mentioned this earlier You can use either a full port 1/8 ball valve or a 1/4 inch standard ball valve FPT  (ball has 1/8 inch port  and will need  a couple of reducer bushings to get it from 1/4 to 1/8 inch pipe. It maybe cheaper too to do it this way  as 1/4 ball valves are more common.  (1/4 brass ball valve is under $10 and you can use it later on a vent tester)

    I thinking of just hooking the valve up between the vent and the radiator and "playing" with it.  When it starts banging you can slowly throttle it down and see if that helps.

    - Rod
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,311
    CHange the radiator valve.

    I am betting the radiator vale is a hot water not a steam valve. Webbs sells both and there is a difference.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Radiator Valve - Steam

    Charlie may have put us on to something here. I looked up Hammond valves and they have a water radiator valve and a steam radiator valve listed. (See attached PDF) The specs are the same so what might be the difference?  The machining? I can't see that they would list / stock two different valves if it was just the seals that were different as the material handled (water -hot or warm ) is the same. It would be more economical to go with the better seal and have just one valve covering both applications.

    I also checked FW Webb's catalog (see attached photo) They also list both types.  You might want to give Webb a call and see if you can find out what the difference is.

    Thanks Charlie!  I learn something new everyday!

    - Rod
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    If the pictures are correct, it looks like the steam has a bigger body to allow the steam and condensate to pass each other. That appears to be the valve he has (by his first post picture)
  • JH_2
    JH_2 Member Posts: 57
    radiator valve

    I found the technical literature for the valve I have on Legend's website

    The steam valve:


    The hot water equivalent:


    From the diagrams you can see that the difference is in the disk - steam has a flat rubber disk and the hot water version has a tapered bronze/rubber disk.   Looking at that what I have is definately the steam version.

    I can still change out the valve to a different brand to see what happens. Nothing to loose at this point.
  • Unknown
    edited November 2009
    Radiator Valve- Steam

    Looking at the valve drawings, if I didn't know which one was which and had to pick the steam valve, I'd probably pick the water valve as it looks like it would have a smoother flow through the valve area. From a design standpoint (and steam isn't my specialty) i can't say I'm very happy with the lower part of the valve as it looks like it would collect condensate. (See attached drawing)  I think I'd see how other brands differed in this area. On the other hand there are obviously many of these valves in use so if it was a problem it would have been changed. The thing that bothers me is that you removed the stem assembly and it still hammered which means something about the interior of the valve (per the attached drawing) OR maybe we're back looking at the radiator?

     Any Pros have suggestions on the best brand steam radiator valve?
  • Big-Al_2
    Big-Al_2 Member Posts: 263
    edited November 2009
    Have a bunch

    I'm not a pro, but I've been moving and adding radiators around my house  I bought supply valves one-at-a-time from the local supply house and also from sellers on eBay. I didn't do it on purpose,  but they have been been five different brands.   I bought one Legend, one Watts, two branded Matco-Norca, one Everflow, and one Hammond.  Superficially at least, they look as though they could have been all made in the same Chinese factory.  All of my radiators are quiet, even the one I bushed down from 2" to 1.5" and undoubtedly created a big puddle in the bottom.  Well . . . if I listen very carefully to that one, I can sort-of hear something like a faint trickle of water inside . . . but no banging.

    A couple valves were bronze and the others were brass.  The bronze valves are priced higher, but I don't know if they are actually better or longer lasting.

    My $.02 . . .
  • JH_2
    JH_2 Member Posts: 57

    Thanks Al, sounds like changing the valve is pointless, eh?

    This is all so strange. 

    I put the vent rite #1 vent on it.  This is an old one, maybe its gunked up but it vents slow.  Below #5 and the radiator never seems to heat at all.  But when it does heat there is still hammer :(

    Yesterday I did an experiment. Left the heat off all day and then turned it up to 70 to make the boiler run a looong cycle (In this mild weather, most of the time the thermostat satisfies before all the radiators heat 100% and fully close the vents).  With that vent this radiator was the last to heat, but now I get hammer in the radiator and some hammer in the runout/riser.

    So maybe the pitch of that runout is a problem after all?  But why would it cause more noise in the radiator itself than in the pipes?

    In any case, for now I'm not ready to spend the $$ to start ripping out pipes in the basement.   I'm just going to shut this radiator off until I have the time/$ to properly deal with it.  The 2nd floor is overheated anyway so one less radiator wont be a huge loss.
  • Big-Al_2
    Big-Al_2 Member Posts: 263
    edited November 2009

    The reason a radiator heats so well is that it has a LOT of surface area.  It might be acting like the soundboard of a musical instrument, amplifying any vibrations transmitted by the pipe.
  • juliachicago
    juliachicago Member Posts: 22
    before you rip out pipes

    try replacing the radiator, or, cheaper yet, swapping it with another one in your house/apartment. as i said, i had a similar situation and no one wanted to believe the actual radiator was the cuplrit, but it was.
  • Raise the Radiator?

    Just noticed the post I wrote around noon today for some reason didn't post so will try again.

    Kind of grasping at straws at this point - Is there any chance you could jack up you whole radiator and pipe a bit?  Usually there's a bit of slack in the pipe below the floor and if you would raise everything even just a slight amount that might improve the pitch situation. Just a thought.

    - Rod
  • mike jones_2
    mike jones_2 Member Posts: 92
    quiet steam

    just wanted u to know that we have an amazingly quiet 1 pipe steam system in a 10 unit building.  we have many other problems and mysterys, but it is so quiet that we wonder if there is something wrong, seriously.  yes it is on, because it heats and we pay the gas bills, but we cant get a 0-5 guage to read any pressure at all, and the vents fill with water every few days, blocking up the radiators from heating until emptied.  sure wish it was a hot water system, steam is 1 tough nut to crack and i cant say i'd recommend it to anyone that doesn't love science!
  • SteamHeat
    SteamHeat Member Posts: 159
    In Case You Haven't Found An Answer

    In case you haven't found an answer to your problem I'd like to ask if you ever hear the "hammer" when your system is off? The reason I ask this is that some of my radiators "clang" from thermal expansion / contraction even when there is no steaming taking place. If I walk past them they clang. If I run my hand along the sections they clang. They're 70 + years old and have expanded and contracted thousands of times and I think that they just have a degree of compliance which lends itself to "orchestral percussion". I am mentioning this so that you aren't chasing your tail if this is what is happening. Maybe I am way off base. I am very new to this stuff, but I thought I'd throw this into consideration if it helps you.
  • JH_2
    JH_2 Member Posts: 57

    I had never noticed the radiator clanging when the heat was off... In fact I once sat next to it during a heat cycle and heard the first clang as soon as the first section got hot.

    Maybe it is thermal expansion... you could be right... but in any case we have had the radiator off for a month and no more hammer...

    ...Well, no hammer in this radiator at least. Yesterday I drained out some mud and topped off the boiler. Then last night the mains were hammering like mad! I think maybe I filled it a bit to high? who knows. today I dropped the water line 1/2" and it just ran for a long cycle and no hammer.

  • Water Line Level

    If the water is too high in the boiler you maybe getting the dreaded "Wet Steam".

    Look in your boiler's I&O manual (if you don't have it you can usually find it on line) and look up the design water line level measurement and mark it on the sight glass and it 's not a bad idea to mark it on the cabinet behind the glass too in case the mark on the glass gets wiped off.

    - Rod
  • JH_2
    JH_2 Member Posts: 57

    Thats exactly what I did.  The water line in the book is 26 5/8 measured off the floor. hartford loop  is supposed to be at 24 5/8.  Well whoever piped this did that exactly - the centerline of the Hartford nipple  is at ~ 24 5/8. I think I filled it a little higher heeding the warning about 2 inch clearance from the loop but on my boiler they also put the centerline of the header exactly 24" from that water line so if I go up any more I'm under that 24" minimum to the header.

    So it seems the water line on this one is very sensitive... but its ok now. 

    Might need a skimming though, as the waterline does bounce (an inch or so) when its steaming...
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