New steam pipe LOUD BANGING!

biglebowski99

I just finished a gut renovation of an apt in New York with a one-pipe steam radiator. The plumber had to replace a steam pipe that was leaking that went from the 6th floor to a small mezzanine/top floor. I know the plumber put in a slightly smaller pipe (3/4" ? instead of 1 1/4"?), but said that should be fine for a small mezzanine room. Now that the building heat is turned on, there is a ton of SUPER LOUD banging coming out of the radiator on the mezzanine every time the heat turns on. Wakes me up several times a night (and the neighbors, sometimes, too!). There is also an annoying tapping (almost like dripping sound) in the downstairs wall where this pipe was installed. The plumber insists that he didn't change the pitch. The upstairs radiator is sloped (slightly) towards the valve, which is 100% open. It is the same cast iron radiator that was in the room before, though it was kept in storage for a year while the apartment was renovated and the plumber installed a new valve and air vent.

Any thoughts on what we might be able to do to control the LOUD CLANGING sounds? The building has about 20 apartments, and my (top floor) apartment seems to be the biggest problem. I can ask the manager to bleed the system. Anything else they should try (adjust pressure, switch radiator?)

Jamie Hall

If he really put in 3/4 inch pipe -- I hope black iron -- it's going to bang on startup. Pretty well guaranteed. In fact, it might bang all the time. The minimum pipe size in the tables I have is 1", and that handles a maximum EDR of 28 for a runout. Pretty small.

KC_Jones

Need to put in the larger pipe, the plumber messed up and should fix it. And honestly should fix it on his dime.

Fred

If it had 1-1/4" run-out to that radiator, why did he decide he could reduce it to 3/4" ? That is too small to supply steam AND allow condensate to return at the same time and is likely too small to support the radiator in that Mezzanine. Additionally, did he reduce that pipe to 3/4" on the horizontal? Depending on how he reduced it, it may hold water.

KC_Jones

You will find after this experience "good enough" with respect to steam heating actually isn't good enough.

Your contractor isn't knowledgeable with steam to have done that, I would recommend you don't ever let them touch the system again at least after they fix this mistake.

JohnNY

Wow. Any plumber working in NYC should at least know that much. Yes, the ¾" pipe has to go. I'm surprised your Super allowed that to happen.

MilanD

Aaaand, there is nothing your super can "bleed". This is not hot water with trapped air.

biglebowski99

Ok, Really appreciate the advice. Right now, by far our biggest problem is the SUPER LOUD radiator banging in the top floor/mezzanine level bedroom.

With that in mind, two important updates:

1) I looked at the drawings again, and the plumber actually installed a new 1.25" pipe (replacing a 1.75" pipe).

2) When I turn off the valve for radiator in the top floor/mezzanine bedroom, there are no more noises in that top floor room. (We actually could sleep through the night, though it was cold up there). Does that help diagnose the problem? Is there something we might be able to do with just the radiator (new radiator, steeper pitch, etc?)

Thanks

Jamie Hall

Ooooops. Unless that new pipe has lots of pitch -- like lots and lots of pitch -- it's almost certainly too small. Probably two sizes too small. There is a reason for certain size pipe for steam, and it's not because that's what he had on the truck.

Fred

New pipe is likely too small to let steam in and water out during a heat cycle. Pooled water will cause banging

KC_Jones

If turning the valve off stopped it, then it is almost certainly not the radiator it is the piping.

At this point pictures of as much of the new piping as you can get would help a lot. Not only the pipe size, but the routing is suspect in my mind. If they can't size it correctly can they even route it correctly?

Steam has subtleties that need to be done correctly or it will never work silently like it should.

neilc

and if the pipe size was changed,
then the valve was changed also,
right?
not only to too small,
but is it even a steam valve?
make sure you get a steam valve on the new pipe job.

biglebowski99

Hmm...I spoke to my plumber, and he thinks the pitch should be sufficient. (see attached photos, from before the replacement). Although the pipe is smaller now (1.25”), the pitch in that section looks around 30 degrees or more. (The new pipe follows the same course and he only replaced between the two elbows, not the 15’ much flatter run on the top floor/mezzanine level).

Still praying that the problem is with the radiator itself since ripping out the finished walls and flooring is a MAJOR project.

Fred

The pitch on that pipe that drops to the floor isn't what we're concerned about. The question is: Is there any pitch on that horizontal pipe overhead, to the radiator?

KC_Jones

Does the pipe I circled have slope? It should have at least 1" in 10' of slope. Also downsizing that pipe definitely doesn't help.

biglebowski99

Let me double-check. Either that overhead pipe wasn’t touched or it should been replaced with the the same slope. (The metal floor joists are 10”, so getting 1.5” of rise in a 15 run should have been easy).

Thanks again, your help has been great!!

Fred

He may not have gotten the pitch on that horizontal pipe because he went under the sprinkler system piping. Do you know how large the radiator is (EDR)? That will help tell if the pipe is big enough. Post a picture of it if you can front view, side view and measure the height.

biglebowski99

Also, I don’t think that overhead pipe was downsized. I think it was always 1.25”. If it makes any difference, there are actually two overhead pipes. The other pipe, which can’t be seen in the picture, ran to a radiator that was removed, so now it is capped at the end of the run.

biglebowski99

Thanks Fred, I’ll take a picture when I get home

Fred

biglebowski99 said:

Also, I don’t think that overhead pipe was downsized. I think it was always 1.25”. If it makes any difference, there are actually two overhead pipes. The other pipe, which can’t be seen in the picture, ran to a radiator that was removed, so now it is capped at the end of the run.

So where is the pipe he reduced? That overhead pipe is smaller than the diagonal one that goes to the floor. looking at the fittings, actually, none of it looks like new work.

EBEBRATT-Ed

@biglebowski99 said: Hmm...I spoke to my plumber, and he thinks the pitch should be sufficient. (see attached photos, from before the replacement). Although the pipe is smaller now (1.25”), the pitch in that section looks around 30 degrees or more.

It really doesn't matter what the plumber THINKS. There are books and sizing charts for steam. If you don't follow the rules trouble almost always follows.

Obviously the plumber knows everything except how to read

Jamie Hall

It's not that piece of pipe with a 30 degree drop that's the problem. It's the one going horizontally across the overhead. Check it.

biglebowski99

As far as I know, he only reduced the diagonal pipe. The other pipes run along the floor of the top level/mezzanine, and I believe are 1.25”. Unfortunately, there is no easy way to check the slope of those pipes. However, I don’t think he touched them except for the last few feet since they ran in between my apt and my neighbor’s apt. For what it is worth, here is a picture of the radiator. It is under a staircase, so I couldn’t get a better photograph. The dimensions are 8.5”x20”x28.5”

Fred

That's a big radiator. I'm betting the condensate can't return while steam is entering the radiator with a 1-1/4" supply. What is the pressure set at on your boiler Pressuretrol ? High pressure will compound the problem.

KC_Jones

biglebowski99 said:

As far as I know, he only reduced the diagonal pipe. The other pipes run along the floor of the top level/mezzanine, and I believe are 1.25”. Unfortunately, there is no easy way to check the slope of those pipes. However, I don’t think he touched them except for the last few feet since they ran in between my apt and my neighbor’s apt. For what it is worth, here is a picture of the radiator. It is under a staircase, so I couldn’t get a better photograph. The dimensions are 8.5”x20”x28.5”

One thing you should get clear in your head, he touched everything. With steam if it is connected to the system and anything is changed then everything was touched. At this point I would be suspect of ever single pipe on that entire run until I found the problem.

Water is laying somewhere and steam is picking it up and slamming it into a fitting somewhere. The only way I see you resolving this is to check and verify the pitch of every single pipe on that run.

The only other possibility is too small of a pipe and the steam and condensate are fighting for space....the steam almost always wins that battle and you get banging.

You may have to be open to the idea of exploring....or just listen to it bang for the rest of the time you live there.

Fred

@biglebowski99 , Something just isn't adding up here. You have said that the plumber reduced this particular radiator run but I can't see where any fitting have been touched, except for a new valve at the radiator and that bushing into the radiator, while it looks like it was removed, for some reason, it looks like the original bushing, so I doubt that the pipe was reduced, unless he only reduced a small portion of the run, somewhere that isn't shown in the pictures. If he installed a reduced section, on the horizontal, overhead, that we can't see, that would allow condensate to pool at the end towards the radiator. What is actually going on here?

biglebowski99

Thanks Fred, the diagonal picture was the “before” picture. Unfortunately, we don’t have any “after” pictures because the wall was covered back up. I posted that picture to show the slope. He only replaced the diagonal section (see marked-up photo with the smaller 1.25” pipe). The only other change he made was moving the radiator about 5 ft in the top floor/mezzanine bedroom. Again, that section is under the wood floors now, but I can’t imagine he didn’t leave at least an inch of downward slope. I also double-checked the radiator this morning, and it has a good pitch down towards the valve. I am also waiting to hear back from our super about the system pressure.

acwagner

I agree with @Fred about things not adding up.

A few things I've noticed. On the radiator photo, it looks like the valve is connected to the original pipe using a coupling and a close nipple. If I understand this right, this is the original radiator connected to the original piping (maybe?). So, if that's the case, it looks like the plumber changed the pitch of the runout pipe somewhere (as in reduced the pitch) and when he went to hook up the radiator back up it no longer lined up by several inches because that end dropped. So he added the coupling and nipple to line it up again. Either that or your finished floor was raised several inches (which I doubt).

In LAOSH, Dan says that for a horizontal runout that is not dripped for single pipe system, the pipe needs to be pitched 1/2" per FOOT. If the run is longer than 8' (which looks like this is) and you can't get that pitch, then use a pipe one size larger. I'm guessing neither happened in this case.

So, two possible options. Change out the radiator to smaller radiator EDR. Or, shut the valve off, disconnect the radiator, and see how much play is in the pipe. Maybe you can regain the pitch, remove the coupling and nipple, and reattach. Or at least put some blocks under the radiator to try and get that pitch back.

Fred

I think you are right @acwagner , it looks like the plumber added a two inck coupling that the valve is mounted on to make up for the lost height (pitch) that the old pipe had.

Jamie Hall

That would do it, for sure.

acwagner

The 1/2" per foot requirement in this situation would also explain the plumber's response about his new pitch being "enough" or "more than enough". As a plumber, he might be thinking pitch requirements for DWV plumbing, which is 1/4" per foot I believe. Not enough in this situation because it's steam, not DWV.

biglebowski99

You guys are amazing! Thanks! He did move the radiator about 5’ and we installed a new floor, which is about at 0.5” higher than the old one, but that 2” coupling definitely makes me concerned the pitch of the pipe under the floor was changed? Good pick-up! I wonder if there is some play so he can pull it up a bit and try to get more pitch

Fred

If the pitch was lost because of that coupling and the nipple, he should certainly have enough play to return that horizontal pipe, under the floor back to its original position. He will have to use a different pipe configuration to remount the valve. Maybe a different length nipple out of the elbow under the floor (If he can get to it) or a male/female coupling and no nipple between the coupling and the valve.

acwagner

@biglebowski99 Do you know which direction the radiator was moved along the runout? As in he removed 5' of pipe or added 5' of pipe to get the radiator in the new position?

biglebowski99

Thanks Fred and acwagner!! You’ve given me some hope.

In terms of direction, the plumber added 5’ +/-

acwagner

If he added length to the runout then it will be less likely there's enough room to pitch the pipe much more. I also would have thought since he added length to the runout that all the fittings and pipe from that point to the radiator would be new. So, I don't understand why he has the coupling with nipple to connect to the valve instead of cutting and threading a piece of pipe the correct length.

Try to pitch it more if you can. If the pitch and sizing isn't right, then you basically need to de-rate that pipe connection. You may have to get a smaller radiator. One that is 28 EDR or less might solve the hammering problem.

Kahooli

acwagner said:

So, I don't understand why he has the coupling with nipple to connect to the valve instead of cutting and threading a piece of pipe the correct length.

Not all plumbers can even do that these days

Kahooli

Here's an idea before you have to tear out the ceiling - take the radiator valve off and push a camera down it and see if you have pooled water anywhere.

KC_Jones

If he added 5' of length and added height then I don't see how the pitch could be right. If the pitch is maintained and the pipe is lengthed the vertical to the valve has to get shorter not longer.

I'd try jacking that rad up as high as I could and see what that does. That will make the rad end of that pipe higher which should give it more pitch.

BTW in case you haven't figured it out yet, the guy who did this shouldn't be working on steam.

Fred

If it were me, I'd simple take the radiator loose at that union on the valve. My guess is you will see that valve and vertical pipe it is mounted on spring up, well above the radiator connection. I'm guessing he put that coupling and nipple and valve on and then pushed them down to where he could connect to the radiator. If it does spring up, that will be proof that the horizontal pipe under the floor is now bowed down at the radiator end and holding water.

biglebowski99

So, the plumber came back after Thanksgiving. Apparently, when he extended the runout line, he drilled through a few joists to get it into the new position. So, there is barely a 1/4" of play to get more pitch. He also put wood blocks under the radiator increase the radiator pitch towards the valve, but that didn't seem to do much. Maybe, we'll need to downsize the radiator, which is unfortunate because that room isn't all that warm to begin with.

Oh well, live and learn....