Help! Banging after a temp. blocked air vent

jg86

Hello, thanks in advance for your thoughts.

Context: I'm on the 1st floor of an old NYC building with single pipe steam radiator.

Incident: The bedroom radiator air vent (not the bullet/Hoffman kind) was making a high-pitched hiss for a while. The radiators/pipes were not making any other bangs or similar noises. Very stupidly (I still feel like an idiot), I tried putting a tiny wad of toilet paper just outside the hole to baffle the hiss. It worked but a few minutes later I saw it got sucked in a bit into the hole (didn't go in) and the vent was very hot. I took it out but since then, banging started coming both during heating and cooling. When heating would start, there would be near-constant bangs coming from underneath the radiator (I think) that would rattle the woodfloor, lasting most of the heating period. Then the entire time it was cooling, every 2 minutes there would be bangs originating from underneath as well. Closing the valve completely stopped the heating banging but had no effect on the cooling-period banging, so I opened the valve fully again. The livingroom-radiator is fine, no problems.

Changes made and effects:
1) The super came in and first turned the boiler off and then on (in order to change the air vent to a Hoffman). This fixed the problem for 1 single cycle, then the same exact banging problem returned. It did fix the hissing problem fwiw.
2) He then pitched the radiator (see pictures attached). This fixed the problem PERFECTLY for 4-5 hours but over the past few days the banging has been slowly returning, which is odd. However: now, instead of the banging originating (seemingly) from under the floor, the bangs sound like they're coming from inside the radiator. And now its 4-5 bangs during heating, and also the same bang every 2 minutes during cooling. NOTE: The floor is higher on one side lengthwise, so now that it's pitched width-wise towards the boiler, the radiator is pitched slightly on two sides.
3) The super checked the pipes underneath the floor and reported no problems and no sagging.

Worth highlighting again that there were no problems at all with noise before I blocked the air vent for several minutes.

Questions:
1) Ideas on how to proceed to fix? Why did pitching work temporarily but then stop working, and why did it move the banging from underneath to inside the radiator?
2) Is detaching and capping the radiator entirely a viable idea, would that definitely stop the banging? I don't actually need the heat from this radiator, the apt is hot.
3) Random - the super said he preferred the radiator valve be partially open. Everything I've read says it must be fully open or closed. Has anybody heard that sometimes it should be partially open? NOTE: I've left the valve fully open, but it hasn't lessened the banging.

Thanks so much for any thoughts, I'm at my wit's end and haven't slept well in a while. I'm not yet sure if the landlord is willing to hire a real plumber (hopefully yes) and the super only knows basic things. Please let me know if there is any info I left out, I'm very new to this.

neilc

you can not close the radiator valve,
it traps condensate, and HAMMERS,
open it back up.
if you need to try and stop the radiator from heating you can turn the vent upside down, back it out 180*

jg86

Thanks Nelic..FYI: I've left the radiator valve fully open since last week, but it has not lessened the banging.

Also: The banging also happens when the heating is off, so I'm guessing turning the vent upside down will not solve the problem fully.

Fred

The radiator should be pitched from end to end, towards the supply valve but it should not be tilted, from front to back. That will allow water top pool in the corner of the radiator sections and cause banging/hammer. I would have to suspect the hammer and the timing with the tissue paper was just a coincidence , unless you happened to pushed down or sat on the radiator causing it to lose its pitch or maybe pushed the horizontal pipe under the floor out of pitch.

Also, on a one pipe system, the supply valve should always be open. Make sure that when you opened and closed it to try and stop the noise, that you didn't cause the disc, inside the valve to come off the end of the valve stem and stick in the steam pipe blocking condensate from getting out of the radiator. That will cause banging too.

neilc

ah thought that was a slam dunk,

it seems you have somewhat a working relationship with your super,
maybe you and he/she can post some pictures down at the boiler, and of the pipes under you,
you're looking for a sag where water is sitting, and how to correct it.
also, what's the boiler pressure doing?
what's it set to and what shows on the gages?
how's the water in the site glass look? dirty?

neilc

another thought,
could still be the valve,
and the disc inside fallen off and sitting there causing same closed valve type problem.
ask super to open valve top and check for disconnected disc on the seat

jg86

Fred said:

The radiator should be pitched from end to end, towards the supply valve but it should not be tilted, from front to back. That will allow water top pool in the corner of the radiator sections and cause banging/hammer. I would have to suspect the hammer and the timing with the tissue paper was just a coincidence , unless you happened to pushed down or sat on the radiator causing it to lose its pitch or maybe pushed the horizontal pipe under the floor out of pitch.

Also, on a one pipe system, the supply valve should always be open. Make sure that when you opened and closed it to try and stop the noise, that you didn't cause the disc, inside the valve to come off the end of the valve stem and stick in the steam pipe blocking condensate from getting out of the radiator. That will cause banging too.

Thanks Fred! regarding your second point: Is this still a possibility given the pitching of the radiator fixed the problem completely for a day? (The valve has been untouched and fully open since pitching).

Fred

@jg86 said: Thanks Fred! regarding your second point: Is this still a possibility given the pitching of the radiator fixed the problem completely for a day? (The valve has been untouched and fully open since pitching).

Yes, it is still the case. If the disc is loose, it can move and bounce around when steam flows and settle differently with each heating cycle.

EBEBRATT-Ed

possibly the disc fell off the valve with all the recent fiddling as @neilc said

neilc

Fred wrote quicker than I do

gfrbrookline

On a scale of 1-10 how loud is the banging and when do you hear it during the cycle, beginning , middle....? Since you are on he first floor you might be hearing heat expansion from the boiler which will be intermittent based on firing frequencies.

jg86

gfrbrookline said:

On a scale of 1-10 how loud is the banging and when do you hear it during the cycle, beginning , middle....? Since you are on he first floor you might be hearing heat expansion from the boiler which will be intermittent based on firing frequencies.

Hello gfr. Regarding the thought about being on first floor: In my first two weeks in the apt there was no banging sounds at all, they started suddenly after the air vent was blocked, so would that not mean that the floor placement is a nonfactor? Below please see a breakdown of the noise, this is all AFTER the super pitched it, which did lower the noise (though I'm concerned its getting worse):

Heating:
1st sound type: 20-30 strong clicks from underneath the radiator in the first minute when heating turns on, loudness is around 2-3. Previous to pitching, it was very loud bangs (7) rattling the floor.
2nd sound type: 4-5 bangs during the first 5 minutes of heating, when the air vent is releasing air, loudness between 4-6.
Little to no bangs during the end of the heating cycle, maybe some clicks.

Cooling:
Bangs every 2 minutes during the length of the cooling phase (about 40 minutes), loudness between 3-6, sounds like inside the radiator. Previous to pitching it came from the floor and loudness was 8.

Lmk if helpful or sheds any light

Fred

The clicking is expansion noise. Check where the pipe comes through the floor and see if the steam pipe is rubbing against the wood floor. The radiator could have been shifted when the radiator was re-pitched. If so, try to shift the radiator enough to get the supply pipe away from the wood floor or slide a piece of plastic milk carton between the pipe and the floor.
The banging is most definitely water/condensate sitting somewhere and being hit by steam. I suspect a lose or broken disc in the supply valve.
I also see the floor is sunken on the supply side of the radiator. You may have to raise that end of the radiator up to bring it back to level with the rest of the floor and then re-pitch the other end to give the radiator the correct pitch. Raising the end of the radiator that is sunken in the floor will also raise the horizontal pipe under the floor and give it its pitch again.

jg86

Fred said:

The clicking is expansion noise. Check where the pipe comes through the floor and see if the steam pipe is rubbing against the wood floor. The radiator could have been shifted when the radiator was re-pitched. If so, try to shift the radiator enough to get the supply pipe away from the wood floor or slide a piece of plastic milk carton between the pipe and the floor.
The banging is most definitely water/condensate sitting somewhere and being hit by steam. I suspect a lose or broken disc in the supply valve.
I also see the floor is sunken on the supply side of the radiator. You may have to raise that end of the radiator up to bring it back to level with the rest of the floor and then re-pitch the other end to give the radiator the correct pitch. Raising the end of the radiator that is sunken in the floor will also raise the horizontal pipe under the floor and give it its pitch again.

Thanks so much for these thoughts Fred! I will share all of them with my super. FYI - there was some light clicking before the pitching and before the initial incident that began the banging, but it sounds like it can be fixed so I'll look into that. I'll have the supply valve disc checked as well.

jg86

Hello, a few updates, The super came yesterday:

1) He declined to check whether the disc fell off the valve because he said that causes rattling but not the intermittent banging that persists through cooling that I am experiencing.

2) He turned the air vent upside down AND closed the supply valve. This hasn't fixed the problem. When the building heat turns on, the radiator does not get hot, but a few bangs still come through.

3) So the banging persists, especially upon cooling (once every 2-5 minutes, starting off louder then getting progressively lighter). He said he will send somebody that can check the pipes underneath - he said the problem must be with the pipes because the banging persists after closing the radiator (true?) - if that is true, then why did pitching the radiator help partially? He said he will try maybe pitching the pipes.

He also said perhaps pitching the radiator even further (to 30-45 degrees) might help -- true?

Any thoughts or counterpoints very welcome! thanks again

nicholas bonham-carter

Only a slight angle is needed for pitching the radiator. If the horizontal pipe under the floor has sagged, then both ends of the radiator can be raised a fraction of an inch to correct the slope.
I don’t know if the possibility of over pressure beyond 1.5 psi has been discussed, but that condition, arising from a clogged pigtail, or main vent, not having been cleaned out annually, can suddenly rear its ugly head, and cause some of the symptoms you describe. Really only a few ounces are needed to get steam up to the top of the system.—NBC

Jamie Hall

If the banging persists more than a very short time after the boiler shuts off -- it's not water hammer. It's expansion -- or in this case, contraction noises. Pitching the radiator may have helped by changing where -- and how much -- the points of contact are.

Intplm.

@jg86 in the picture that you have provided, it shows that you have a piece of wood under only one leg. Find another piece of wood or brake the one that is there in half and put it under the other leg next to it so that you can have a more evenly dispersed draining of the condensate from the radiator. The way it is now can allow condensate to pool up in the back of the radiator and cause some banging.
The thoughts about the valve are valid. It could be chattering from the disc inside.
The tp in the vent. It might still be there? (however unlikely). Changing the vent might help. Fixing the valve is another probable cure. Do get the radiator pitched properly and see how much that helps first.

BobC

One of my upstairs radiators didn't heat well. I replaced the air vebt abd checked the piping in basement for slope. The radiator itself was dead level so I shimmed it up on vent end and that seemed to help some.

The fix was to shim the input side 1/4" and the vent end 1/2" using plywood strips, it heats just fine now. When lifting a radiator I use a 2X4 as the lever and a block as a fulcrum, this lets you lift gently and not screw up your back.

Bob