one pipe venting - main vs return worth it?

Bob W._3

Sounds like a non-issue. You already have main vents; they are just at the end of the return. No big deal as long as you don't have water hammer in the return.

GeneHav

one pipe vent - main vs return - is it worth it?

One main vent is 25'x2" - return is 25'x1 1/4" the vent is installed on the return vent (horton #75). The other main is 12'x2" - return is 1 1/4" the return vent is a barns & jones. (about the size of a horton #4) Both mains heat up within 30 secs of each other. What would I gain by installing the vents at the end of the mains? We are only talking 25' and 12' of return. In order to install main vents I'll have to remove the asbestos covering and break apart 80+ year old pipe or drill out the main pipe and weld on a nipple for the vent. I have looked at many 100 yr boilers and all of them have the vents on the returns. (we have a lot of old houses in the Boston Ma area to look at). I have to think that the dead men put them there for a reason.

Steve Garson_2

All you gain is the latent heat lost from heating the return. In my opinion, if your returns are insulated, don't change a thing. If they aren't insulated, then insulate them. Don't mess with the asbestos.

GeneHav

The returns are insulated and since the radiators are about 20' from the mains (2nd story) I can't see where installing main vents would help. I gain maybe 20 secs by installing main vents vs return vents.