Venting Radiator Risers

Mike_SteamEfficiency

As part of a master venting project, I want to properly vent the top of each riser. The building is a multi-family pre-war with 1-pipe steam. Each bathroom has a blind riser. There are one and two bedroom units.

Can I assume that all the radiators branch off from the blind riser, so that I can rely on venting the top of the blind riser alone?

How common is it that some or all radiators have their own riser that much be vented by the top radiator (presumably by adding a vent immediately prior to the radiator valve)? Note that in the basement, I can see at least 40 risers going into the ceiling and the building has 10 unit on each floor and thus 10 blind risers.

And if I cannot rely on the blind riser branching to all the radiators, it there any way to guesstimate which radiators are not branched off the blind riser (perhaps based on the number of risers in the basement; or perhaps only the closest radiator to the blind riser)?

Thank you,
Mike

Steamhead

How many floors in this building?

Mike_SteamEfficiency

4 floors. Other similar buildings we are working on have 6 floors.

Steamhead

Here's one way to do it, on an exposed riser- see the last pic in the series:

https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc

On a concealed riser, you'll have to rework the piping at the radiator. See page 118 of Lost Art for one way to do this.

My guess is the building has mostly concealed risers, otherwise you'd see them as they go up thru the rooms. Many times the risers are in the outside walls- on steam, you didn't have to worry about water freezing in those pipes (and that's another reason our company does not convert steam systems to hot-water).