Bang

anthony_3

I have one radiator in my whole house that gives a bang every 3 or so minutes after my once pipe steam system has shut down and is starting to cool. I have tried everything, i flushed the returns, I tilted the radiator etc. Still it gives this bang every time during the cool down. The radiator is off the second riser from the main line. The first riser is dripped directly into the a wet return that heads into the boiler. I also have a dry return running along the mispoint of my basement wall. Could the drip be causing any problems? I read that you should drip into the dry return with a loop seal. From what I can tell, this is dripping directly into a pipe on the floor that leads into the boiler after it joins with the dry return below the water line and runs along the floor to the boiler.

Bob Gagnon plumbing and heating

is the shutoff

to the radiator open all the way? bob

ed wallace

banging

sounds like water trapped in base of radiater

anthony_3

Yep the valve is opened all the way and the it has been replaced using the correct size. Is it common for radiators to have water trapped in them? Should I just flush it?

anthony_3

Is this common? I have it tilted quite a bit. How can I test it? Should I just shut the valve and operate see if the banging stops?

Mike T., Swampeast MO

Valve replaced

with correct type? There must be a difference because hot water and steam valves are offered. I believe steam valves will work with hot water but not vice-versa.

Jeff_4

After shut down sounds more like the pipes or the rad contracting. I used rubber furniture coasters under one of mine that did the same thing. It worked like a charm!!

anthony_3

Yep... Its a Steam valve. When you talk guys talk about water hammer during the cycle. How often does the bang occur? How do you determine exactly where the bang is coming from since it could resonate in the pipe?

Thanks
Anthony

Mike T., Swampeast MO

If contraction is causing it

You might also try UHMW (ultra-high molecular weight) plastic under each leg. It's almost like thick Teflon. Available in woodworking catalogs and stores.

Unknown

Anthony

Any way to post some pics of the piping in the basement ? Usually a banging radiator is a syptom and not the true problem . Is this radiator connected to the header with the dry return ? Does the dry return have a main air vent , and is it working ? Does the other header with the wet return have a main vent also ? I think bad vents are the main cause of problems on any steam system the worked properly in the past . One other thing - does it look like the dry return is pitched down towards the boiler all the way ? As long as the dry retun tees back into the wet return below the water line , you wont need a loop seal - have to admit I never heard of it before . Steam is tricky - keep us posted on what happens .

anthony_3

Thanks for the detailed questions Ron! I will post some pictures tomorrow of my system. Hopefully you will be able to see somthing. As for your questions...

The dry return does have a main vent but its burried behind a finished wall. No way to test unless i cut a hole. The dry return is pitched towards the boiler very slightly. What about the drips I mentioned? (one cold one hot) any ideas?

anthony_3

dry return...

I checked my dry return with a level. It seems it is perfectly horizontal (level). The reason I checked this is because I felt the dry return before it turned into a wet return and it was cold. When I slid my hand along the dry return it eventually felt warm. Does this mean condensate is having a touch time moving down the system? With this condition, when would I have water hammer and where would it likely occur.

Jeff_4

My dry return...

pitches down toward the boiler...makes sense to get the condensate back to the boiler. Mine is HOT as the steam starts to give up its ghost and becomes a liquid returning. Can you flush your wet return. Maybe there is some sludge down there that needs to come out. Plus...as you felt the return...where was it warm?

Unknown

Yep , the dry return should be pitched down

toward the boiler - so the condensate can return without laying in the pipe . A totally horizontal pipe will give you some problems . But the first thing I would do is find a way to the main vent and change it . I know its in a tight spot , but you will want to make it a good area and keep it accesible anyway - those main vents need changing every few years .

The dry return might be taking a long time to get hot just because of a bad main vent , but if there is still the same problem after changing it - I would try pitching the pipe - someone here should have the specs for a dry return . I think it might be an inch per 10 feet ?

Unknown

Yes , you can flush your returns

And you wouldnt believe how much crud comes out . What we do is install a valve to isolate the return pipes from the boiler , and put a drain in to get out all the spooge . It usually takes a good 4 hours to pump all the crap out of the returns under steam pressure . This is a job with 2 returns .