What’s causing this rad noise?

heatinghelp819

We have steam heat single pipe system. I’m trying to figure out if this noise is just from metal expansion within the rad itself (which I won’t be able to fix) or if it’s water hammer or something else that can be fixed. Happens for a couple minutes when the heat comes on, and is a little louder and longer in the morning when the rad is cold from the setback.

This is in a bedroom so would love figure it out if possible. I’ve pitched the rad with no change; valve is fully open. (It has a gorton D because it’s at the end of the run, but the room gets very hot so may reduce to a gorton 6 but not sure this would help the noise). Thanks.

https://streamable.com/alpa8k

Paul S_3

Thats water hammer. The valve may not be fully opened or broken off . You may also be running higher than normal pressure. What pressure is the system running at? You can check that at the pressure control.

heatinghelp819

Pressure is the lowest I can set it at, .5. Valve is fully opened. A faulty air vent wouldn’t cause this if the rad is getting fully hot right?

Paul S_3

A faulty air vent or a air vent that's too small for the radiator and piping run out would be the cause of the radiator not getting fully hot. But it will not cause water hammer. I would make sure the pigtail is not clogged below the pressure control. I would also check the pitch of the main this radiator is connected too and also the piping going to this radiator. If that's all good, it's a strong possibility that valve may be holding water in the radiator causing the hammering. I see a lot of systems with back pitched piping holding water, steam will not go that way especially at a low pressure. Eventually as pressure builds it will push the water and cause hammering, heating only part of the radiator

heatinghelp819

I was thinking the Gorton D is too big and was thinking of replacing with a 6, not sure if that’d help. Maybe steam is coming in too fast.

The system was just serviced and everything cleaned out. This rad has a small horizontal pipe at the supply that goes straight into vertical piping all the way to the main in the basement, whose pitch looks ok. I guess that leaves the valve. Could it be noises within the radiator itself from metal expansion?

Paul S_3

The noise is water hammer from what I hear. Expansion is more like a ticking or rubbing sound.

Jamie Hall

Critical timing question: is this water hammer before — possibly just before — you feel steam at the inlet? Or is it after the radiaror starts to warm? If it's before — even slightly before — you feel steam at the inlet, it's somewhere in the runout or the main in that vicinity.

heatinghelp819

the sound starts just as the cycle starts; I know the supply/inlet is warming up but it sounds to me like the sound is coming from the radiator itself - I’ll have to double check to see if any of the first panels of the radiator are warm when I hear the sound. Will report back.

Jamie Hall

The radiator is a huge speaker. It will happily amplify a water hammer in the pipe which is connected to it, but if steam hasn't gotten there yet it's very unlikely to be the actual site of the problem. Look for a runout which isn't adequately pitched — or pitched the wrong way even.

heatinghelp819

this radiator is on the second floor, has a very short horizontal pipe that runs to the vertical riser that goes straight down two flights to the basement main that is horizontal. Here is a photo.

heatinghelp819

heatinghelp819

Ok, the sound starts just after the cycle starts, when the supply pipe has already gotten hot and the radiator is starting to warm up.

Jamie Hall

If it's not expansion (it still might be) check and make sure that the valve really is fully open. Otherwise, it might be incurable — just a little water trapped between the valve and the elbow going up to the radiator.

holograham

Is this really water hammer? I have a few radiators that make a similar sound and I always thought it was thermal expansion.

heatinghelp819

valve is definitely fully open.

We’ve lived in this house for almost a decade and many of my radiators have always made this noise, and I always thought it was the metal expanding too…