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Adding vent to 45 degree riser towrard end of supply line

Frederick Member Posts: 19

I have a 12 flat arranged in 4 stacks, ABCD.  Boiler in basement of stack A.  There are three dry returns at the boiler from branches from the steam supply pipes.  Stack A has one, stack B has one and Stack  C and D share one.  The return on C/D has four Gorton #1s.  I have temperature sensors in stack A and D.  Not surprisingly Stack A (70-75F ish) is hot and stack D is about 5-10F colder.  Being the penny pinching SOB I would like to lower the temperature in A to a maximum of 70F, but the softy in me won't lower D below 65F.  Therefore, I would like to introduce a vent near the last riser in D.  I was contemplating replacing the 45 degree pipe in the last riser with a tee with perpendicular hole pointing up and attaching vents. Before I start trying to turn 70+ year old pipes, I figured I'd solicit comments.

Thanks in advance,



  • Jamie Hall
    Jamie Hall Member Posts: 21,097
    edited March 2011
    Not quite sure...

    I can visualise how a T on a 45 degree riser can wind up pointing straight up -- but maybe I need another cup of coffee.  That said, it really doesn't matter all that much were the vent is hooked up, provided -- and a very important provided -- it is hooked up so that it is out of the direct shot and splash of a slug of water.  A bad location is right at the end of a pipe... not bad is a T a few inches to a foot short of the end or ending elbow.  I would think that coming off a 45 degree riser and going up a bit would be fine.  Any handy unions there to help you undo the whole thing?

    I might add that if you can get at the top of the riser (I'm assuming bottom feed?) that's an even better place for a vent used to speed up a riser...  I've also seen a big vent on the INLET side of the last radiator on a riser sometimes.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Polycarp
    Polycarp Member Posts: 135
    I did it like this

    I did something similar.  It was a less than ideal solution for me and I have since changed it. 

    One thing that is less than ideal here is that the Tee meets the angled pipe on the topside.  That means that some condensation could potentially drip into the steam and wet it somewhat.  A better solution would be to have the Tee exit on the side, so that any condensation would flow into the bottom of the angled pipe.
  • Frederick
    Frederick Member Posts: 19
    Hmm, condensate

    I guess its a good thing I asked,  I did not contemplate the condensate getting reintroduced into the steam.

    Did you realize a significant improvement in getting steam to that part of the building?
  • Polycarp
    Polycarp Member Posts: 135

    I did, until the main drip clogged .. flooded main means vents don't matter.  Since I had to replace that drip, I moved the vents all the way to the end of my main
  • Frederick
    Frederick Member Posts: 19
    main drip??? end of main???

    Sorry If I am a bother but...  I am not completely familiar with the lingo.

    What is the main drip?  Is this the where the pipe containing the steam drops vertical and becomes a return pipe?

    By end of the main are you referring to just after the last riser or where the steam pipe becomes only a return pipe?

    My situation is after the last riser in basement D the steam pipe becomes a 2" pipe with no other connections all the way back to the boiler where it drops into the hartford loop.  The time between the steam pipes leaving the boiler becoming painfully hot to the point dry returns become painfully hot is greater than 10 minutes in the C/D loop where the A and B loops are painfully hot in about 2 minutes.  I assume that pushing the air through this 80+ feet of 2" pipe so that it can be vented at the boiler is a main contributer to this delay and the fact that stack D is about 10F colder than stack A.

    I naively assume that there will not be more condensate by venting at the last riser, just that the condensate will be produced sooner. no?

    Thanks in advance,

  • Polycarp
    Polycarp Member Posts: 135
    wet vs dry

    I have a wet return, so my main terminates at an elbow with a vertical pipe that drops below the water line (the vertical pipe is a drainable mud leg that I added to keep my drip from getting clogged again).  With a wet return, the vents go at the end of the main before it drops down to the wet return.

    Since you have a dry return, your system is a little different, but the vents should still be just before the main turns from dry to wet.  You may just not have enough venting on your main.  That is the first thing to check.  Just four Gorton #1s for 12 flats just seems a bit slim to me. 

    jpf321 has put together an excellent worksheet for calculating your venting needs (you can search the wall for it). 

    If you do have enough venting, and D is the only one not getting hot, putting the vent at the riser take-off may not do you any good; it would essentially be just more main venting.  12 flats with 4 risers, I'm assuming 3 story?  If main venting isn't your problem, you'd likely be better off venting at the top of D.  That will get the air out and the steam in faster.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    I was thinking the same thing

    C and D both need to drop below the water line separately. If they are tied together above the water line, it doesn't matter where you put a vent. One side will still vent faster than the other due to shorter run. 
  • Polycarp
    Polycarp Member Posts: 135

    Good point.  A pipe diagram and pictures would help.
This discussion has been closed.