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# Two vents on one radiator, single-pipe steam system

Member Posts: 1
Hello! A plumber suggested we balance our building's single-pipe steam system by having two vents on certain radiators (on the hot side of the building). This plumber helped us get much better balance with some work last spring, and now we're fine tuning. Sadly he is now not returning our calls, so we've called someone else to try and implement the work. The plumber who can implement the work is saying the way to have two vents is to use some type of t-fitting at the existing location, and then the two vents would connect to that fitting. This seems weird to me, so I started to do some research.

I saw Dan's article on this site regarding multiple ways to help balance a single pipe system, explaining one technique as follows: "Use two vents on oversized radiators. Oversized radiators are always a challenge. No matter what size vent you use, that vent will close once the steam reaches it – even if much of the air remains in that huge radiator. The Deadmen often faced this challenge by drilling and tapping those oversized radiators for a second air vent. They positioned the second vent a few inches lower than the first. The two vents then worked together to let the air out. When steam reached the first vent (the higher of the two), that vent closed. But the second vent (at the lower level) continued to vent air from the radiator. As a result, the radiator heated more completely, and brought the Deadmen a step closer to system balance. This trick can work just as well for you."

This one-vent-below-the-other explanation makes sense, and the t-fitting suggestion I don't really get. Am I correct to think the plumber suggesting the t-fitting is just a knucklehead, and ask him to place one-vent-below-the-other?

• Member Posts: 8,423
Add a second vent to radiators on the hot side of the building? Steam will take the path of least resistance and added vents on the hot side of the building will only get steam to that side of the building even faster. If you are going to use a second vent, it should go on radiators on the cooler side of the building and you can put it on the side of the radiator opposite the existing radiator vent. That will vent air out of the risers faster and close when steam hits it, leaving the original vent to only have to vent air out of the radiator itself. That will bring steam to the cooler side of the building quicker or you should be able to use slower vents on the hot side of the building and faster ones on the cooler side of the building. First thing to do is make sure you have the right amount of large vents on all the mains that feed the building, then fine tune with radiator vents.
• Member Posts: 8,139
Definitely increase the main venting first.
If you have a low pressure gauge, you can see the resistance or back-pressure of venting, which should be lower than 2 ounces.
This will fill all the supply mains first, and then the radiators simultaneously. Gorton #2’s or big mouth vents are popular.
If you have a large system, with several dry returns, it may seem expensive, but believe me, it is an investment, which will pay off in comfort, and reduced fuel use.—NBC
• Member Posts: 5,680
Why would you think that it's a knucklehead that would do this? What can't you grasp about it?

Bob Boan

You can choose to do what you want, but you cannot choose the consequences.
• Member Posts: 306
This old radiator does not need a second vent as the tapping is near the middle of the radiator.

On the cold side of the building you install Gorton C or D vents. these are reasonably higher capacity vent valves than the average radiator vent valves, On the hot side of the building you can install smaller capacity vent valves. Like Gorton #4 or 5 or five vents.

The best way to test this is to do the top floors radiators first and check the results. This can be done by you without a contractor.

Jake
• Member Posts: 15
Hi [email protected], I am very interested in this topic, so I want to make sure I am understanding what you said.

I have this huge radiator, and want to make it heats quickly. Are you saying to remove this screw here and add an air vent right?

Regards the screw thread, is that the same of the air vents? I am asking because I am afraid of removing the screw and if the air vent doesn't fit there, after I could have problems to put the screw back.

• Member Posts: 2,263
edited January 8
Trust me: you're going to have a lot more trouble removing that plug than putting it back in. As for whether you should add a vent, that depends on where this plug is located. Different radiators come with various optional tappings for different applications. Can you post a picture so we're sure what you're talking about?
Just another DIYer | King of Prussia, PA

1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
• Member Posts: 15
Somehow the picture was not posted before.. see now

• Member Posts: 2,263
Assuming this is a single-pipe radiator, the vent should be at the other end. If the radiator isn't heating fast enough, you might want to try a faster vent. A vent in the valve side of the radiator might help fill the riser with steam faster, but once it closes, you'll be venting the radiator through the vent at the other end, so it's probably not worth trying to get the plug out.
Just another DIYer | King of Prussia, PA

1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
• Member Posts: 15
This radiator is located on the 3rd floor.

The steam boiler has two main pipes, one with dry return (that connects to this radiator) and other that has wet return.

The main pipe with dry return doesn't have main air vent, and there is no way to install one. As the pipe (1 1/4 size) that connect to the main pipe to the radiator is very long, I assume there are a lot of air that needs to be vented.
• Member Posts: 306
Vent valves must go on the opposite side of the steam inlet.

Normally when a second vent valve is installed on a radiator it is installed below the existing vent valve.

You would have drill and tap the radiator to install a second vent valve.

This should be done by a qualified mechanic that will be responsible for damages if he fails to do it right. Normally a 1/8" tap is done because the vent valves are threaded for 1/8" tappings.

Try using a gorton C vent in placed of the existing vent valve.

Jake
• Member Posts: 1,623
I don't know, Jake. As @Hap_Hazzard indicated, you could have one really fast vent (like a C) on the valve side. It would close when the steam first got to the radiator. Then you could have a slower vent on the far side of the radiator, to let the radiator slowly fill after that.
1 pipe Utica 112 in Cedar Grove, NJ, coal > oil > NG
• Member Posts: 2,263

I don't know, Jake. As @Hap_Hazzard indicated, you could have one really fast vent (like a C) on the valve side. It would close when the steam first got to the radiator. Then you could have a slower vent on the far side of the radiator, to let the radiator slowly fill after that.

Actually, I was saying that, since it would only be effective in venting the supply piping, it probably wouldn't be worth doing unless you have an unusually long runout/riser. If you just have a big honkin' radiator, you need a bigger radiator vent, or maybe two in extreme cases where you've already put the slowest possible vents on your other radiators.

I was thinking that, in @rikmonteiro's case, it wouldn't be worth it because the supply pipe is only 1", so there's not a lot of air to vent.
Just another DIYer | King of Prussia, PA

1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
• Member Posts: 15
[email protected] I already tried the Heat Timer Variavalve (0.516 Venting Capacity) and Maid-O-Mist "D" 1/8" Angle Air Valve (0.341 Venting Capacity). As I said, I have to vent all the air from the pipe that goes from the basement to the 3rd. floor through this valve in the radiator.

Note: Vent Capacity from https://heatinghelp.com/assets/documents/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-1.pdf
• Member Posts: 1,623
edited January 8
I hear you @Hap_Hazzard. I was speaking somewhat generally, but also a little specifically since Rik's radiator is on the third floor. But at only a 1" supply I agree there's not much there to vent.
1 pipe Utica 112 in Cedar Grove, NJ, coal > oil > NG
• Member Posts: 2,263
@rikmonteiro, What size vents are on the rest of your radiators? If your fastest radiator has anything faster than a #4, you need to start there.
Just another DIYer | King of Prussia, PA

1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
• Member Posts: 8,423
A lot of discussion to get back to what I said in the very first response to the Poster. But the reinforcement is always good.
• Member Posts: 15
@Hap_Hazzard For this main pipe that has dry return, one radiator has a "Maid-O-Mist 4", and the other two has Home Depot Air Vents. All these radiator are heating ok...

As I said, the problem that I have is the other main vent (the one with wet return), the radiators (around 12) are even heating. It would be a lot of work to change of them, to delay it.
That is where a second valve would improving the venting on this problematic radiator.

BTW, this is the main pipe with dry return.

• Member Posts: 2,263
Interesting.

Since I don't seee a main vent on the main, I assume it's probably somewhere on that dry return? This isn't optimal, because it's effectively turning the dry return into a radiator, because the steam will continue to fill the pipe as long as it has a vent to push the air through.

If that return does, indeed, have a vent on it, try removing it and plugging the hole. This will force all the venting on this main to occur through the three radiators while forcing more steam into the other main. This may cause the boiler to cycle on pressure, but it will give you some idea about what needs to happen to achieve balance. If this helps get steam to the problem radiator, we need to think about how to speed up that other branch without slowing down this one.