Missing Main Vent

Don1450

I have a 1-pipe steam system in a small house I have 5 radiators coming off of a single main/return circuit. The total length of the loop is about 18 feet (9' out and 9' of dry return). It is all 2' cast iron pipe. I have vents on all radiators but no vent on my main/return. is this bad??? I would like to put one in during a boiler replacement that will happen in the next week or so. I assume my plumber will put it in at the end on the return run to avoid cutting into pipe at an earlier point in the loop. Is this ok? Can someone tell me if there is an easier way to cut vents into the main besides removing all that pipe? Can the pipe be drilled and tapped? Is there a special cut in fitting?

KC_Jones

First when it comes to a steam install I wouldn't "assume" the plumber will do anything. Is it in the contract to balance and/or address your venting? It is always a good idea to have vents on the mains even a short main like that. I would say if you got it at the end of the main a single Gorton #1 would be good, possibly 2. Do your radiator vents make any noise now? If they do that is a good indicator you need the main venting.

Fred

If you have to put the vent down towards the end of the return, use a Gorton #2 or multiple Gorton #1 s as you are doubling the amount of pipe you are venting. In any case, the vent(s) need to be after the last radiator feed.

Captain Who

What about putting the vent(s) at the beginning of the dry return, or perhaps set back a little to avoid water hammer? I have a situation personally where there is no fittings on the mains (2) for a vent but the original installer put the vents at the end of the dry returns. The house is about 1934 era. My thinking is that it is so difficult to cut into the mains and weld in a fitting to the iron piping and it can't be set back 15 in. from the end since there are two vertical takeoffs just several inches from the end for risers leading to radiators. On the other hand, my returns look to be brass (not copper) and that would be a fairly doable soldering job for me to put a nice T with a 3/4 threaded boss (or maybe 1/2) for a vent "antler".

Sorry to butt in but maybe this is helpful for the original poster too.

Fred

At the beginning of the dry returns is good. there really is no reason to vent the dry return, except where that is about the only practical place to put a vent.

Don1450

How do you put a vent into the beginning of the dry return? How do you break into the main loop? At least at the end of my return I can take a union apart and unscrew a few lengths of pipe and elbows to insert a threaded coupling that could accept the vent. Below are some photos. 2 show the return to the back of the boiler and 1 shows the main.

Fred

Some people drill into the pipe or fitting and have a welder weld a threaded adapter over the hole so that a nipple can be mounted.

KC_Jones

Looking at your pics, unless I am seeing it wrong you have 2 mains not one? Is your new install going to address the mains being tied together like that? They should be hooked into the header independently not through a tee as they are. If that isn't a second main I am seeing what is it? There isn't a reason to vent the dry return, but if that is the easiest place to put it I wouldn't think it's the end of the world, you just need to use a larger or more vents than you would have to if it was at the end of main. I am not sure if there is any functional reason not to do this.

Don1450

That second small pipe that you see coming off the vertical just above the header goes directly to a radiator on one side of the house. It is not another main that is feeding more radiators. In this case is it acceptable?

Abracadabra

#1 - It's not "cast pipe" it's called black pipe. cast iron pipe is used as soil pipe, not for steam.
#2 - If you are putting in a new boiler, that small pipe should be piped directly into the header, not teed off the main riser like that. That'll reduce the velocity of the steam coming out of the header into that main. Not too much I guess since it's only feeding a single radiator with probably no main vent.

KC_Jones

And it should probably be the last thing off the header before it turns down to the equalizer since it is functioning as a counter flow pipe. Don't want it dumping condensate for the main to pick up, which is probably going on now with that set up.

Don1450

I understand now. Thanks!! I'll definitely specify that this pipe has to be brought off of the header directly and as close as possible to the equalizer to minimize condensate flow into the fresh steam from the boiler. This makes great sense to me. They're going to need to remove a lot of this piping anyway during the boiler replacement since I'm going to get a Burnham Mega steam and it has a back exiting flue. This will change the position of the boiler quite a bit. Since the radiator pipe in question is not tied directly to the main should I put a vent on it or will the vent on the radiator be enough?