Piping on removed one-pipe radiators?

Ed59

Hi, we've got a 1905 two-family Victorian near Boston with a single steam system. Our unit on the first and part of the second floor has mostly two-pipe radiators with air-vents. The other unit on the second and third floors has one-pipe radiators.



The other unit has decided to separate the systems and put in their own hot-water/air system (we know we need to replace our boiler so it's not oversized).



Their plumber has disconnected the pipes in the basement that went up to the one-pipe radiators. What he's left in several places is a pipe that comes off the steam main, goes to a T where the old pipe went up (now capped off). From the bottom of the T a pipe runs down to the return. So there are now several loops of pipe that go from main horizontally a bit then right down to the return.



Question is, does this make any sense? Is this highly inefficient or will it cause water hammer from the steam going right to the return without any radiator? Or any other problems? Should these loops be removed and capped off at the main and return instead?



Thanks!

Jamie Hall

Two pipe

with air vents is a little unusual... and very very old.  Are you sure that that's what it is?  Some pictures of the radiators would be illuminating,..



As to the capped risers, they shouldn't be a problem -- so long as the return to which you are referring is a wet return; that is to say, below the water line of the boiler.  Those were drips for those risers.



Now if they go down to a dry return, that's not good.  So we need to know...

Ed59

two-pipe air vent

Pretty sure. There are air vents on all the radiators. The return pipe is smaller than the supply. There are two valves at the bottom of each one. The valve in the return doesn't look like a trap to me. Pictures attached (the valve on the supply side is missing it's handle on this one).

Ed59

wet return

The return is definitely lower than the water level in the gauge.



Why is it not inefficient to be running steam through this big loop of extra pipe in the basement?

Jamie Hall

Yep, two pipe with air vent

that is a lovely antique system!



It isn't particularly inefficient to be running steam through those loops simply because there is very little steam running into them -- only as much as the line itself will condense.  If those lines are insulated, that's not very much.  The steam can't go anywhere at the end, and without vents on the line the air can't get out of the line at the end, so.. not much steam wasted.