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Radiator making banging noise

Dezso3Dezso3 Member Posts: 11
A few minutes after the thermostat turns the boiler on, and the radiators begin to heat up, some of the radiators in my house (not all of them) will occasionally make a really loud bang, as if you hit them with a hammer, and sometimes you can feel the resonance going through the floor. This is really annoying because sometimes I wake up at a very early hour and then can't fall back asleep. What could be causing this?


  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,535
    new water-hammer problem in radiator

    first of all, is this a new problem which has suddenly appeared? if it has not recently started, can you think of any changes which have been made to your system before  this water-hammering started? could your steam pressure have shot up, beyond the point of no return [24 ounces].

    this could be caused by your main vents having become inoperative, and therefore forcing the radiator vents to do all the work, along with higher pressure caused by a clogged pigtail.

    dirty/oily water in the boiler,  perhaps from some pipe work, can cause the steam to pick up too many water droplets, as it leaves the boiler on its way to your noisy radiators.

    in addition to describing any changes which have been made, why not post some pictures of your boiler, and its steam piping [including boiler make and model].--nbc
  • Dezso3Dezso3 Member Posts: 11
    Re: Radiator making banging noise

    Well what happened was we had our old boiler replaced, and afterward the pipes starting making an extremely loud banging noise (water hammer), so we called the contractor who had installed it, and they managed to fix it. However, one of the radiators was also modified. It had been shut off for quite some time, probably about one year. The living room was getting really cold though, so we decided to re-open it. We also installed a Gorton No. 5 vapor equalizing valve on it. What is very bizarre is when I turn the thermostat on during the day and set it to 70 degrees, I can't hear that particular radiator making any noise. However, for two nights in a row I woke up for seemingly no reason, and when I put my hand on top of the radiator cover, it was hot, so it had to have made a noise in order to wake me. Overnight, the thermostat is set to 65 degrees, so I don't know if the colder radiators warming up to the same temperature vs. from 70 degrees while heating up has anything to do with the noise. =\
  • jpf321jpf321 Member Posts: 1,558
    the only thing that makes sense....

    this seems to make sense to me .. but since i haven't experienced the noise, nor have you directly either since you only say it "wakes you up" .. is that during the day, the coldest that the rad gets is around 70dF .. and that at night, it gets 5dF cooler .. or maybe even cooler depending on where it is in relation to the thermostat .. and being that it is a living room rad, it's probably pretty big .. so what i'm thinking you are experiencing is expansion sounds .. and the expansion sound if occuring during the cooler night rather than the warmer day .. i think that's the only reason why t-stat temp would have any effect on the sound (rad) ..

    did you know by the way that a setback (temperature difference) of greater that 3dF on the t-stat is reported to waste more fuel than it saves? i will be running some tests myself in the coming days .. but that's what's been floated anyhow. many people here in the forum do not have any setbacks greater than 3dF or in your case .. no lower than 67...i'd even suggest 68 depending on how you have your t-stat setup.

    Entire Site | MAIN WALL | Strictly Steam | Off-Wall

    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm

    venting worksheet download | Lost Art Of Steam Heating | my NEW system pics | my OLD system pics | old patents | pipe size chart | Copper Size Chart: K,L,M

  • Dezso3Dezso3 Member Posts: 11
    Re: Radiator making banging noise

    We just called out a service technician to see what the problem is, and he said that the problem lies in the pipes being pitched poorly, and that the water isn't able to flow back to the boiler, which causes water hammer to occur. He then offered to correct the pitch of the pipes so that water can properly flow back to the boiler for $1800. Is this a reasonable price for such a job, or should we hire a different contractor?
  • Dezso3Dezso3 Member Posts: 11
    edited January 2010
    Pipes making banging noise/water hammer

    Lately what I have discovered is that the pattern of banging is completely random. There is no telling when the pipes will make noise. Sometimes when the heat turns on one of the pipes leading to a radiator in the living room will make on large "bang!" and then be silent for the rest of the heating cycle, and sometimes when the heat turns on that same pipe won't make any noise. As I said earlier, it's completely random. Every single day I wake up at around 5:30 in the morning when the heat goes on, and cannot fall back asleep until school starts at 7. So if I go to bed at 11, then instead of sleeping 8 hours like I should, I only sleep 6 1/2 :madhell: If I weren't so sensitive to noises while asleep then it wouldn't be a problem in the first place. A contractor said he can redo the pipework so that the pipes are pitched properly for $1800, but my dad doesn't want to pay such a large sum of money. Any suggestions as to what I should do?:wall:
  • jpf321jpf321 Member Posts: 1,558
    first thing to do ..

    really determine if it's hammer or expansion .. expansion can be random since the pipes aren't always cooled to the same temp for each cycle. and it would normally be heard only once at beginning of cycle. expansion, where it is rubbing against wood or something, can be helped by inserting plastic milk container pieces where the rubbing is occurring.

    being pretty handy myself, $1800 sounds like an awful lot of money that can buy quite a few $5 earplugs.
    Entire Site | MAIN WALL | Strictly Steam | Off-Wall

    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm

    venting worksheet download | Lost Art Of Steam Heating | my NEW system pics | my OLD system pics | old patents | pipe size chart | Copper Size Chart: K,L,M

  • Jamie HallJamie Hall Member Posts: 6,654
    I suppose...

    that the real question is: how handy are you?  It is very likely that your plumber is right -- that the pitch of the pipes is not correct.  That is far and away the most common cause of water hammer banging at or near the beginning of a cycle.  Assuming, as jpf mentioned, that it's not expansion.  But it is easy enough to check.

    I have to assume that this is one pipe steam.  OK, then.  The idea of the game is to make sure that the water from condensation in the radiators can get back to the boiler without pooling anywhere, or being unduly held up.

    First off, the valves where the pipes come into the radiators must all be open.  All the way open.  Part way open will almost guarantee banging.

    Second, the radiators need to be slightly pitched towards the inlets.  Not that much -- but at least slightly.  You can repitch them by placing quarters under the feet if need be.  Check with a level; don't even try to do this by eye.

    Third, all the horizontal pipes must also pitch back towards the steam mains in the basement.  This pitch needs to be at least moderate -- a half inch per foot is usually recommended.  Again, don't try to do this by eye.  Use a level.  If you find a badly pitched length of pipe, see what can be done to make it right.  Maybe raise the radiator somewhat?  Different situations call for different solutions.

    The same pitches apply to the pipes in the basement.

    The steam mains, from which all the radiators are fed, must also pitch so that the water can drain.  Sometimes this is back towards the boiler.  Sometimes it's to the far end, where there will be a pipe going down and then back to the boiler (there should also be a vent there, but that's for later).  Either way, the pitch must be consistent -- no low spots or sags!  Hangers can and do sag.

    A lot of this can be do-it-yourself, if you are moderately handy.  It is possible that some of it isn't, or that you may be reluctant to start moving pipes.

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

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • BrianBrian Member Posts: 237
    Maybe not so random

    Not sure whether this will be helpful, but 5:30am can be the coldest time of day. When you say that you can't fall back asleep until 7, you don't mean because the radiator is banging the whole time do you? If you do, that would suggest to great of a set back on the thermostat, as was already suggested.

    Do you think that the radiator is loudest in the morning or that it's actually banging all day but you don't hear it because there's background noise then?
    1929 Ideal Heating vapor system.
  • Radiator Slope

    Follow Jamie's advice and check the pitch of your radiators and make sure they are slightly sloped towards the inlet pipe to "encourage" the condensate (water) to drain. The valves have to be either fully open or fully closed. If they are half way the incoming steam collides with the outgoing condensate.  Do you have the books- "We Got Steam Heat" and "The Lost Art of Steam Heating" ? They're available in the Shop section of this website (see the top of the page) These are a "must" if you own a steam system. Check the radiator slope first and see what that does and then we can go on from there. As Jamie said you can do a lot of things, like slope, on a steam system yourself, however, there are some things best left to a pro.

    - Rod
  • FJLFJL Member Posts: 354
    edited January 2010
    Hammer or Expansion

    This sounds like a water hammer.  I say that because OP says that the hammer occurs after the radiator heats up.  An expansion sound would occur as the feeder pipe heats up when steam first arrives, before the steam has an oppty to enter and heat the radiator.  Also, expansion sounds more like clicks and clanks as opposed to a single hammer. 

    I had this problem in a radiator in my bedroom.  The cause of it was a back pitched pipe underneath my bedroom floor.  I paid a P & H person $1500 to replace and repitch the pipe.  I also had to hire someone to break through the ceiling of the room underneath to expose the pipe and to repair the ceiling after the new pipe was installed.  Just to give you an idea about the cost, another contractor wanted to charge me $3000 to repair the pipe. 

    If the problem is a back pitched pipe -- rather than something else, such as the valve being partially open or the rad not being pitched toward the valve, as described above -- I don't think that there is too much you can do to solve the problem.  I lived with a back pitched pipe for several years before getting around to fixing it.  Our problem was not water hammers but water getting clogged and pushed into the radiator, which would prevent the radiator from heating and cause the air valves to spit water.  I got a water hammer sound only when we turned off the inlet valve for both radiators connected to the back pitched feeder pipe, because the trapped water didn't enter the radiator to make room for the incoming steam. 

    I sympathize with you though. 
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