Steam system, dry return main vents

Andrew_22

Indeed, people look at me funny in Arlington when I say "y'all"....

I've got another few inches of clearance between the joists, so I could punch a hole and extend the vents. Worryingly close to the subfloor, and even though the steam is supposed to be dry, I am concerned about steam warping the floors in that area (the piano is right above it).

I think the vents have been sized properly, based on a brief discussion at metpipe of the size of the house, number of radiators, and operating pressure (0.5 - 1.5) of the system.

Thanks for the tip about moving vents back a bit from the turn. If I go for this change, I'll call a plumber--I'm okay with screwing stuff together, but not comfortable cutting into black pipe.

I'm hoping that I'll get some improvement--even if not perfection--just be replacing the vents and moving them up without moving them back. If that's the case, can one buy off-the-shelf parts to get the vents higher up, or is this all custom cut black pipe?

Andrew_22

replacing main vents on dry return steam system

Hi Folks,
I've discovered that the main vents on my steam system are ancient and need replacing. I have a one pipe, parallel flow system with dry returns. The only main vents are atop the dry returns, right by the boiler. The returns make a 90 degree drop right by the boiler, and the mains are located right on this 90 turn on a tee, but the mains aren't up on a nipple, and from what I've read, it's critical that they be up at least 6". Alas, my basement doesn't have much space, maybe 4" up to the ceiling. I have purchased the replacement valves from a good place (metpipe in cambridge, ma). Is it safe for a skilled do it yourselfer such as me to replace them? What additional parts (nipple, coupling, etc.) should I use to get the main vents up another few inches? I have 1.5 inch dry return pipes, and the main valve is currently in a tee coupling where the dry return drops 90 degrees down to the boiler. I am somewhat concerned that I may damage the pipes when I remove the old main valves.

Thanks folks, y'all are the best.

andrew zimmer
arlington, ma

Brad White_203

First of all...

NO ONE from Arlington uses, "Y'All". Just does not happen. Ya heah?

Hi Andrew- I am in Auburndale so not far at least.

Can you open up the ceiling in that area and locate the vents there (create height by going up between the joists?)

It is safe to do so if you use common sense. Switching the boiler off is always a good idea for example! Have a Plan B in place and know your limitations. A "creak" sound is OK, a "crack" or "tink"? Not so much.

You also want to pull your vents back from the ends, using elbows and offsets so that a charge of condensate does not crash into the end tee and up into your brand new vents, directly.

Met Pipe is a good outfit. Which vents did you buy? Did you size them correctly?

Brad

Brad White_203

Moving Vents Back

Hi Andrew

Moving vents back, if you use the tapping you have, is not that big a deal. By that way, I mean you would start with a street elbow (male one end, female the other), then extend a nipple some distance, say at least 8 inches, a foot if you can. Then start a series of tees and nipples, each with a vent, or a single tee and plug if only one large vent.

Each tee would have as tall a nipple as you could fit, in order to maximize height.

This is not entirely "the right way" but has worked well in systems where otherwise you do not have wet steam and a host of other issues. Using a union is probably necessary because of tight constraints. Make up the "antler" on the bench then install it with a union connection, as one way.

What I am describing is all off the shelf fittings and nipples. Anything else is probably "field threaded" but sometimes the fitter may get lucky.
Unless right on, there is a tendency to "spring" the piping to "fit the fittings". This is just so wrong.

"The Right Way", as you note, does mean cutting into that last pipe section, threading in a nipple, union and properly set back tee with elevated nipple for the vent. You got that.

If in doubt, or just because, go hire your fitter. I bet they could use the work.