Banging - steam boiler 1-pipe system

ksd99

First, I really appreciated all the help that you all have given me in the last 2 years with my boiler – it has made a difference. I need some support regarding an issue with some banging. I have a riser that is in exterior wall that goes to the second floor, which connects to 2 rads – one in a bathroom and one in a bedroom. The issue is there is banging in the floor when the steam 1st comes up the riser; I think the pipe is hitting the floor but not sure. I put in adjustable vents and slowed the steam down thinking that might help – it did not make a huge difference. I then closed the vent to the bedroom rad – still noise. I then switched the process and closed the vent of the bathroom – perfect no banging just silence. Thinking the pipe from the riser to the bathroom rad might be sagging, I pitched the rad at the valve side thinking some tension might help – it did not. Any thoughts? I cannot get to the piping without taking up the flooring or going thru the ceiling on the 1st floor.

ethicalpaul

I think your search for a sagging pipe is the right one. The banging is likely caused by water lying in the pipe causing the steam to collapse to vacuum when the steam hits it. It only happens at the start of the call for heat because the water eventually heats up and stops collapsing the steam.

I ended up abandoning my riser in my exterior wall and running a new pipe next to the interior surface of that wall (as I later found out it was originally built!)

You might have to open a hole in the ceiling to find out for sure

nicholas bonham-carter

Sometimes, raising all 4 legs of the rad, while still maintainIng the proper slope, will improve the pitch of the lateral horizontal pipe, so as to make it drain properly.
You could do 4 quarters under the valve end, and 6 under the vent end, for instance.—NBC

BobC

I had to raise a radiator on the second floor a few years back. I put a 3/4" strip of plywood under the vent end and a 1/2" strip under the steam input end.

Houses settle as the get older, i used a 2x4 and a fulcrum to lift the radiator. This allows you to do it gently and it will also tell you how far up you can go.

Bob

Grallert

I used to carry a pile of washers about the size of quarters for adjusting radiators.

ethicalpaul

These can work if you're lucky. I raised mine 2 inches and it made things better (reduced banging), but there was still water lying in the runout.