Mystery- One radiator making a hammering loud sound at beginning of cycle

Alexnyu10

I have a one pipe steam radiator system. It’s overall working really great right now, boiler is new (2021) and have it serviced annually. Brand new Gorton vents on all radiators recently installed too. Heating is even and working great. Just one fly in my Chardonnay.

This one radiator, about 6-7 minutes after the boiler turns on, makes this hammering sound for about 30 seconds, and then after that all is good. Maybe I am asking too much, but I would love to get rid of this sound.

Attached is a short clip with audio.

To the wonderful experts in here, would this sound be caused by the wrong Gorton vent size (this one is a C), the need to drain the radiator, or the need to better level the radiator?

Another clue is if the radiator is already warm when the boiler turns on, it will make this sound slightly but it is quieter. If colder the radiator is when the boiler fires, the louder the hammer.

Final clue, the sound distinctly comes from the side of the radiators where the one pipe comes into it, not the vent side.


https://imgur.com/a/YU4hMGF

(Link with audio)

also bonus question- if anyone reading this knows or is a steam expert and services the Flatbush Brooklyn area, would love to have you do our annual boiler maintenance and correct this at end of summer. Our current plumber is great but NOT a steam expert, and I have not been able to get a response from anyone listed in the directory here (I assume because it’s such a small system and job).

Jamie Hall

Several folks on the directory service your area. @JohnNY . Maybe @EzzyT ?

As to the clang and bang. Classic. Somewhere in the line of piping from the steam main to that radiator there is a section which is not pitched adequately to drain — either too flat or perhaps even pitched the wrong way. It may not be right at the radiator… but you'll need to find it and correct the pitch.

leonz

Hello and good morning Alexnyu10,

As Brother Jamie has said so eloquently you apparently have a problem with drainage of condensate back to the boiler.

Start by looking at the suspect radiator.

If you have a long aluminum bubble level lay it on the top of the suspect radiator to find out if it is level, if it is level it needs to be shimmed on the end opposite the pipe connection to insure it drains back to the boiler.

If after installing the shim or shims under both legs the radiator still bangs, the pipe feeding the steam to the boiler needs to be checked for the minimal slope needed to drain back to the boiler and there are a number of ways to correct it if needed.

If there is enough head room above the steam pipe you can place the level on top of the pipe or hold it under it with a helper to check the pipes slope back to the boiler.

Alexnyu10

good morning and thank you so much

@Jamie Hall and @leonz

Quick question, is there any chance the air vent being sized incorrectly could be causing this or is that really not a possible explanation? The non-steam expert insisted on putting a C on this radiator, but I am suspicious that a 5 or 6 would be the better choice. But it is also possible this is completely unrelated and since the radiator is heating beautifully it does potentially have the right vent, the only reason I am suspicious is this sound seems to have worsened after the installation of the new vent

Regarding leveling, I just checked and it looks like right now it is pretty much flat when I measure with a leveler, so I definitely can try the idea of giving it the slight incline towards the valve. The only issue is this radiator appears to be far too heavy for me to lift on the one side. This might seem like a silly question but is this the kind of thing that requires two strong men to lift the radiator on one side to slide under something to lift that side up? Would you recommend I save that for a plumber or is that something a mere civilian like myself and a neighbor could attempt to do?

BobC

L use a block of wood as a fulcrum and then a 2ft 2x4 as a lever to lift radiators gently and then slide in a spacer to hold that end up. You can do each end separately. I cut 1-1/2x10" slats of plywood (usually 1/2 and 3/4") thick, these can be stained to match the floor.

Bob

Jamie Hall

The various vent choices have much more to do with how fast and how completely the radiator heats than anything else — it might make a small difference to the banging, but very little. So don't worry about that.