Old 2-pipe air vent system?

gbailey

I recently joined the condo board of an 11-unit condo. One unit (the top floor furthest from the boiler) gets far less heat than anyone else (including the units directly below it). We're trying to diagnose and fix the problem and everyone we've had in has said the same thing: we're missing radiator traps throughout the building and we need to vent the mains.

The building was built in 1910 and it's got an old steam system that I THINK is a two-pipe air vent system. All the main radiators (see piping diagram below) have shut-offs on both sides with vents on the return side and no traps. There is no venting on the basement mains. Instead all the venting is on the 4 main risers and on each radiator. The riser vents look seriously undersized to me, but the other 3 risers get heat flawlessly.

So a few questions: 1. can anyone confirm if this is an air vent system? 2. thoughts about things to check? 3. anyone in the Brooklyn area with experience with these systems want to take a look in person?

Thanks for any help.

KC_Jones

Looks like 2 pipe air vent to me. Anyone saying to put traps all over the place where there were none doesn't know what they are talking about.

Most (if not all) true 2 pipe systems that are built with traps have the steam inlet at the top of the radiator not the bottom.

Another way to confirm 2 pipe air vent is the drip pipe, or condensate return pipe should be at least 1 size smaller than the feed. So if you have 1 1/4" pipe in, you should have 1" pipe out.

How many floors is the building? Doesn't make sense to me if all those risers are the same height and diameter to have different venting on them. I would say you need a Gorton #2 vent for every 2-3 floors or so, depending on ceiling height and assuming 2" pipe.

gbailey

Yep. 1 1/4" in and 1" out. It's a 4 floor building with 10.5' ceilings so ~45' vertical rise with 2" pipe.

I'm pretty sure the current vents are the result of some half-baked "repairs" over the years.

KC_Jones

I would suggest for the vertical run alone you need a Gorton #2 vent, big mouth would probably be even better. If those verticals all have their own horizontal runs in the basement you might be able to handle all the venting on the verticals. If the basement mains feed more than one vertical it might be better to handle that venting in the basement.

Some of the pros that have dealt more with this may be along with more insight on venting that type of building.