How much pitch is needed if a larger pipe is used for a run-out?

Bob Altshuler

I just moved into a house with one-pipe steam and I'm having some problems that are being caused by a run-out to the up-feed riser for a 2nd floor radiator being pitched the wrong direction. To complicate matters the run-out passes over a major support beam.

For risers that aren't dripped The Lost Art of Steam Heating specifies a pitch of half-inch per foot and says "In runs over eight feet long where you can't get this pitch, use the next largest pipe."

My question is how much can you decrease the pitch if you use a pipe one size larger?

In particular, it might be possible to pitch this run-out 1/2 inch or maybe 3/4 inch in the right direction over its entire 12-foot length, but would that be enough?

It goes through the ceiling in a spot where it would be awkward to put in a drip directly below the riser, so I think the other option would be to change the piping of the run-out to either go below or around (both above and below) the support beam and put the drip where it goes under the beam, as described in Lost Art in the section on running steam mains around obstructions.

Thanks in advance for any suggestions,
-Bob

bob young

min. pitch

if you just break the bubble on a torpedo level you should be o.k.