Main Vents and one Cold Return

tom67 · December 17

Heating System Short Side - Cold Return.png

I have two questions, the first is the vents on the mains. The vent on the long side looked like it was leaking, rust stain running down the pipe. I then noticed no Teflon tape, so I took it off, taped it and put it back. The next time the heat kicked on, steam released from it. I've never heard this before. I order two new vents, Maid O Mist, #1, 3/4" x 1/2 Main Vent Valve. Would this work at both locations? I also have a third vent location. Its tapped into the end of the long side main elbow. Is that normal?

The second question, I need to add water at least two times a day. I notice that the short side main return pipe is cold to the touch just below the tee vent and before it mixes with the long side return. Could I have a blockage in the pipe? The system piping is old.

Thanks in advance.

Steamhead · December 17

How long are those mains?

ethicalpaul · December 17

There's a lot to unpack in your post. I'll just answer one of your questions for now: the 2nd vent you have at the downturning elbow is not necessary (and in fact is detrimental).

You can just use the vent location that is upstream from that one on that main.

tom67 · December 17

Heating System Long Side.png

I updated the image, but about 9'-2 on the short and 28'-10 on the long

tom67 · December 17

ethicalpaul, are you saying the one that is tapped into the elbow? If so, would I remove it and then how to “patch” the hole in the elbow?

There is currently three vents. One on each return drop (reducing tee) and then the one on the elbow. I would just keep the two at the tees?

Next question would be what size vent should go at each tee. The purchased two replacements but I started reading a book on steam heating and thinking they should be different.

And your close to my area, I’m near MetLife Stadium.

ethicalpaul · December 17

Yes, this one on the right (where the main turns vertical) is unnecessary and unhelpful because you don't need steam in that horizontal pipe that is between the two vents. You can focus all your venting for that main on the vent position on the left.

In my opinion you would be fine with a single Maid o Mist #1 or Gorton #1 on each main. (but see below)

If you remove the vent on the right you can put in a 3/4" NPT plug to close the hole there. Available at a big box store or supplyhouse.com

Looking closer at your situation on the left vent, they have drilled into the fitting and are using a radiator vent. That can be OK because a size D radiator vent is the same capacity as a #1 main vent. Someone did that because they knew that filling that long horizontal part with steam was unnecessary.

But it would be better if you or someone else made the hole larger to 1/4" NPT instead of what currently looks like 1/8" NPT, and used some 1/4" fittings to raise up the vent away from the main pipe a few inches.

I ride the bus past Met-Life stadium every day 🙂

tom67 · December 17

ethicalpaul thanks for the info.

I like to complicate things since I do not like inheriting others work. I am also reading The Lost Art of Steam Heating to hopefully learn something new.

It makes sense about the vent on the right, its at a long pipe run but I'm sure it was the original vent location so it was out of the way. The vent on the elbow was most likely added later.

Here's my overthinking:
Option 1: Replace the elbow with a tee so I can extend the main to install a vent
Option 2: Eliminate the tapped vent (#3) on elbow and install a tee closer to the main and plug the other vent (#2). I'm thinking similar distance on the short side, 12" from the main.

Option 1.png

Option 2.png

Or take a deep breath and just increase the tap to 1/4" and add some piping to increase the vent above the main and plug vent #2.

EBEBRATT-Ed · December 17

I don't agree. Keep the vents on the tees. Make sure they are sized properly and don't put the vent directly on the tee. Raise it up as high as you can with a nipple and a coupling. You want to keep it above the water.

Remove the one tapped into the elbow and replace it with a pipe plug. The one on the elbow is likely to get water in it and not work well anyhow.

Not only the length of the main is needed but the diameter of the pipe is needed as well. You may need multiple vents at each location.

ethicalpaul · December 17

I would take option 1. But don't make the reducing tee as in your photo, orient it like this. Or utilize one of the alternate locations I indicated. Large pipe is much harder to mess with so one of those other locations might be much easier.

My good friend Ed's plan is fine too, and far easier, but I don't like to fill pipe with steam unnecessarily.

I do tend to think that the risk of water getting into a main vent is considerably over-feared. There is no "slug of water" getting shoved down the main by a massive force of steam that we read about in TLAOST or on this forum. It gently flows along the bottom of the pipe and the sides of vertical pipes.

Surging is quite violent and can fill the mains with water, but if you have that problem, the main vent is in trouble regardless of attempts to isolate it.

An interesting test of your situation there would be to remove that radiator vent out of the tapped elbow and fire up the boiler to see what happens. The air will vent out first, then steam will appear and you can see if water shoots out in some dramatic way. I might get proven wrong, which I wouldn't mind at all!

JUGHNE · December 17

Could your short main be sloped the wrong way?

That is could the condensate be flowing back to the boiler in the main pipe and not the return pipe, leaving it cold?

This would be a counterflow main and might cause water hammer.

tom67 · December 17

https://forum.heatinghelp.com/discussion/comment/1827437#Comment_1827437

I added an image in a post above but the mains are 2-1/2", returns are 1-1/4" and I think the branches are either 1" or 1-1/4". Branch are either hidden in ceiling and / or insulation.

The short side main is about 9'-2" and the long side is about 28'-10".

The pipes to me don't seem to be pitched at all. This system has been here for years, I purchased the house 18+ years ago and the house was built before the 1950's. So it's probably be like this since day one.

The system is generally fine, it goes from cold to too hot. It could be the sofa blocking the radiator in the living room but that's another battle. The other rooms feel hot but the room with the thermostat (living room) is cool so it keeps running. Again another battle.

tom67 · December 17

tom67 · December 17

What would be the proper slope? I dont know if the pipes are sloped but it would have been this way since I purchased the house 18+ years ago and the house was built around 1950's..

I dont hear a water hammer so not sure if that is the issue. I think the pipe could be clogged with crud of an old system.

tom67 · December 17

Ed / Paul

What would be the proper vent if I just had vents at locations #1 and #2?

I will get a 4" or 6" nipple for each. The #1 location will be tight since there is a gas pipe in the way.

EBEBRATT-Ed · December 17

If your going to take the elbow off that is tapped for a vent and replace it with a tee orient the tee so the branch of the tee is taking in the steam from the boiler.

@tom67 If you have an obstruction in the way you can offset with nipples and elbows 45s being better than 90s if possible

ethicalpaul · December 17

Based on my experiments, I would put a #1 on each position. Others will say you need 3 Gorton #2s on each one 😅

Why would you position the tee that way, Ed? I don't think I've ever seen a picture of an end-of-the-main tee that is like that. I know in near boiler piping it's against the law to feed the middle of the tee (the bull, right?), but I can't picture why for a vent tee.

tom67 · December 18

@ethicalpaul after some reading, I also noticed the Honeywell Pressuretrol seems to be set high. Based on the photo, is that a correct statement and should I set it to 0.5? The dial seems correct.

ethicalpaul · December 18

Yes, I would put the front setting to as low as it will travel, but don't try to force it lower.

And the dial looks like it might not be at the lowest setting, but is maybe turned some degrees away from "1", see if it will turn so "1" is pointed right to the front (at the end of the dial's travel)

That will get you to a nominal 1.5 psi cutout and a .5 psi cutin, but it won't actually be those values because Pressuretrol devices are horribly calibrated from the factory

JUGHNE · December 18

Slope for parallel flow steam mains is 1" in 20', not much, just enough to get the water running to the return drop.

Your drawing indicated this system is piped for parallel flow.

If some of it is counter flow then the water would flow back towards the boiler.

If you have 2 1/2" mains then there may be not problem with water hammer.

Pipe slope can change over time because of hanger failure or house settling.

May be hard to tell by eye, you need a 2-3' level to check.

tom67 · December 20

https://forum.heatinghelp.com/discussion/comment/1827634#Comment_1827634

The drawing is for my own record keeping / documentation and I didn't add slope to the pipes nor check.

Once the season is over I can perform a deep check and my adjustments to the actual piping system.

tom67 · December 20

UPDATE:

I lowered the CUT-OFF pressure on the pressuretrol from 3 to 0.5 and the system seems better already. I dont seem to be losing water as much.

I also plugged the tapped air vent, and raised the other two air vents plus added new air vents.

Thanks for the help. Glad I found this resource.

ethicalpaul · December 20

Looks great and congratulations! yeah for sure, low pressure hides so many sins! On my system every joint is normally dry but when I run my dumb video experiments and raise the pressure to 3 to 5 psi, they sometimes start dripping

Main Vents and one Cold Return

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