Added a false water line now hammering

JStar

If you'd you like an in-field consultation, I'd be happy to help. Sounds like a strange issue.

Jamie Hall

If your steam mains drop into wet returns with no crossover traps to the dry returns, you absolutely have to have vents on the steam mains. Otherwise you are asking the radiators to do all the venting, which they may not do. If all the traps on a main are closed, presto -- no venting. Then you immediately start to build pressure in the main with no place to go.

One possibility which occurs to me is that you just might push enough steam down that sloping pipe to open the check valve which then might close abruptly and hammer.

I like the idea of replacing both check valves with a water seal loop down the floor. More elegant, if nothing else.

scottnjr

@jamie hall. I hear ya, but this system never had vents on the steam main ends, only the dry returns venting through the rads and it heated and now after the FWL it heats beautifully, so unless I can get rid of this hammering by putting in vents on the mains, I don't see where they're of any value here.
I too thought the check might have been abruptly closing, but I removed the guts and it still hammered.
I also don't want to reinvent the wheel here, just get it back to where it was before our guys put the boiler in 7 years ago. Building water seal loops on the end of the mains would take a day and require opening a finished wall in the basement. If it didn't need them before, I hesitate to add them now only to turn it on and hear hammering again. There already is a water seal there now because of the FWL which I find even more elegant, but I must have something wrong in the height of it. The only difference between the old and new was the old had a higher water line. No other components were removed by us.
The thing that looks wrong to me is shown on the left side of my diagram. A plumber ran 3/4" copper from that low point of the supply and return for a radiator he installed on the second floor. He also put a vent up there that serves to vent that whole side of the house. Due to the short distance between it and the new waterline, I wonder if the vent is intermittently blocked by stacked up condensate.
The main vent I removed was installed by us after all these problems began trying to fix the original problem of not heating which it didn't accomplish. The vent was only about 4' out on the main away from the boiler. That thing was closed long before any rad got steam.
At 2 oz pressure though the hammering is less pronounced at least.

Jamie Hall

I was just thinking out loud... bad habit of mine. The fact that the hammering is less pronounced at 2 ounces, and the fact that it happens rather late in the cycle, both suggest to me that somewhere, somehow, water is getting into a line which is handling flowing air or flowing steam without being able to drain freely. Without being there, though, I can't go much further than that.

scottnjr

Yeah. It's tough to fix something via someone's description. But thank you for your mental calories burned.

scottnjr

Problem still not resolved. I am going back to check all traps when my tempilstick comes in this week.

scottnjr

I just wanted to put closure to this on the wall. I was able to resolve this that same year. I drilled/tapped the last elbow of the steam main and installed a vent. previously, all venting of that main went up to second floor where a previous guy ran 1" copper to a radiator. It has now been 2 seasons and the system is quiet and heats quickly and evenly. One of my greatest heating achievements! It is so satisfying when you can finally fix something after so much effort. Thanks to all who contributed.