Steam Main Vent

bmma

I have a single pipe steam system and I have a question about the main vent. My system seems to be pretty well setup and balanced and I get even heat throughout the house, and everything has been functioning well. But, just recently I noticed that the vent at the end of my main seems to be letting some steam pass through. I'm seeing some steam coming from the vent when the boiler is firing. I assume its likely just dirty and not closing properly. Assuming I need to replace the vent I looked online for a direct replacement, but can't seem to find any info on this particular model (pic is attached). As I mentioned the entire house heats evenly and I'm not getting any banging, water hammer, etc. so the vent seems properly sized. From what I've read on this forum I get the impression that having "too much" venting isn't really a problem but "not enough" certainly could be. So, does anyone know what I would use to replace this vent to get equivalent or higher venting. I'm afraid if I replace it with something too small I'll mess up the balancing of the system, and my wife and kids won't tolerate a cold house for long. Thanks!

bmma

By the way, the vent is vertical in real life but for some reason it rotated when I posted this.

nicholas bonham-carter

You definitely need a new main vent, and the old one should be placed in the heating museum here.
Can you measure the diameter of the threaded connection, so you can put on a Big Mouth vent, or two?—NBC

JUGHNE

That is unique, is each part the same size?
An original venting "antler" perhaps?

bmma

nicholas bonham-carter said:

You definitely need a new main vent, and the old one should be placed in the heating museum here.
Can you measure the diameter of the threaded connection, so you can put on a Big Mouth vent, or two?—NBC

I'm not at home to measure it, but I think the tapping off the 90 is 3/4 inch and is reduced to 1/2 inch where the "antler" is threaded in. I should have plenty of clearance to change things out and get the new vent up above the end of the main a bit, I just want to be sure I add enough venting capacity.

nicholas bonham-carter

You can never have too much venting, so start with one big mouth, and check your pressure of venting, as the air is being pushed out. Keep adding vents until the backpressure is below 2 ounces.—NBC

Steamhead

That vent is kind of unique. I'd love to get my hands on it to see why there are two pieces on one manifold.

How long is the steam main, and what pipe size is it?

Erin Holohan Haskell

Here you go:

ethicalpaul

*Decorative only

bmma

Steamhead said:

That vent is kind of unique. I'd love to get my hands on it to see why there are two pieces on one manifold.

How long is the steam main, and what pipe size is it?

When I finally change this thing out I'd be happy to send it to you.

As for the piping, I'll measure before I do anything but I estimate it's about 70ish feet of 2 inch pipe. If my math is correct a single Big Mouth would be more than enough to handle that.

Fred

Two Big Mouths would be better, on a 70 ft. main.

bmma

Did some measurements and actually found I have only about 45 feet of main. I don't know why I thought it was much longer, chalk it up to getting older I guess.

Fred

One Big Mouth will work, then.

JUGHNE

Perhaps one side an air vent....that was slow to reopen...and the other is a vacuum breaker to allow air back in the system?