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Replacing main line vent

Pin Member Posts: 61
Thanks for the response!

The main line vent is less than a foot away from the elbow (approx 8 inches measuring from the center of main vent to end of elbow) . I already noticed this problem but not sure if it is worth the headache to try to move it 4 inches. However, it is elevated at least 6 inches above the main.

I have attached pictures! These are not quality pictures but it is the best I can do now.



  • Pin
    Pin Member Posts: 61
    Replacing main line vent

    I have noticed that once the steam starts traveling through the main line, it would move slowly across. The end result is that the radiators near the boiler heats up completely as the radiators furthest is just about to receive steam. To my knowledge, the steam is suppose to travel very fast across the main line to where the main line vent is and travel up through all the riser at the same time so as to heat the radiators together. I believe the main line vent is not working properly. Am I correct?

    If so, how do I replace the main line vent? Is it just a screw in kind like the air vents on the radiators?

    Also, I believe I only have one 2" pipe main line about 25 feet and wet return. This is a 3 family house with total of 13 radiators to heat. Is one main line vent enough? If not, is the cost/benefit of adding the 2nd vent to the main line reasonable?

  • Brad White_203
    Brad White_203 Member Posts: 506
    Venting the Main

    Most main vents are similar in function to those on your radiators, just larger.

    It does sound as if your main vents are either not working or are insufficiently sized, or both.

    The nipple for most main vents is either 1/2" or more commonly, 3/4" in my experience. Posting a photo would help get a better "read" on your potential approach.

    For general sizing, your 25 feet of 2" pipe holds about 0.6 cubic feet. A Gorton #2 would vent that in less than half a minute and a Gorton #1 would vent that in less than two minutes at very low pressure.

    Personally, I like using multiple #1's on a "tree" to enable me to adjust the venting rate by adding or subtracting vents.

    One key thing is, forgetting the best vent you can buy- is it properly protected by being held back from the end elbow by at least a foot or more and elevated at least 6 inches above the main?

    The best vent will not last a day if improperly installed at the end of a main where water, steam and crud may race into it.

    Indeed, the steam wants to move faster than a walk when properly vented. The goal, as you stated perfectly, is to have all of your radiators get hot at the same time.

    I would add that perhaps your near-boiler radiators are too well vented and those might be cut back a bit, should they still beat the furthest radiators in the heating race once the furthest ones are better vented.
  • Brad White_203
    Brad White_203 Member Posts: 506
    You are right!

    Those photos really do stink :)

    Being eight inches back has me less concerned than if the vent was right on the top of an up-down tee, that is for sure.

    Given that you have the classic mushroom vent, you should have room to install a lateral antler or menorah arrangement which allows more but smaller vents and also more protection by changes in direction between the main and the vent. A Gorton #2 would work if you can fit it, but if not, I would split it into multiple smaller vents. Please see the attached and see what you think.

    As a practical matter, the first nipple riser should have a union in it, to allow the menorah to be pre-fabricated and installed as one piece. You are not likely to get a wrench up in there, that I can see.
  • Fred Harwood_2
    Fred Harwood_2 Member Posts: 195

    Here's a photo of a Gorton #2 main vent, the biggest and best of mains vents. You won't need to tee it, and Steamhead can tell you where to get them, if your local heating supply store doesn't carry them.

    This vent is a master at rapid venting of your steam main.

  • Brad- My computer says that your attachment is a CFM file rather than a PDF. If it is the one I think it is, that is a neat picture

    Internet supplier for Gorton Vents - if you can't find a local supplier
  • Brad White_203
    Brad White_203 Member Posts: 506
    Try saving it

    as a PDF file. I think you have it though! Not sure why it sometimes comes up as a CFM file.

  • Brad- No luck I'm afraid
  • Pin
    Pin Member Posts: 61

    Thanks for the PDF, but this arrangement seems way too complicated.

    Which do you think is more efficient? Gorton #1 or #2? I see Gorton #1 costs about $19 while Gorton #2 costs $53. Is it even worth it to buy Gorton #2 for that much considering that I can just vent with Gorton #1 at double the time but more than half of the price?

    Also, can you tell from the poor pictures which size I should buy?

    Oh, and do I just unscrew the old main vent by hand and screw the new one on with teflon tape just like a radiator air vent?

    Sorry for the many questions. Thanks!!

  • A Gorton # 2 has over 3 times the venting capacity of a Gorton # 1.

    Good main venting is important. The sooner the air is replaced in your mains by steam, the sooner steam gets to the radiators. Also with good venting on the main, the radiator vents just have to vent air in the pipe leading from the main and the radiator itself.

    Venting capacity depends on the size of the threaded opening in the main. On a 1/2 inch vent pipe you can use two -Gorton #2s ganged together.
    On a 3/4 inch vent pipe you can use up to four- Gorton # 2 and one Gorton #1. This would achieve maximum venting for that size of pipe. (This is from Gerry & Steve's Vent Capacity chart)

    Yes, they are basically screwed in like your radiator vents (or any other pipe fitting) though it pays to mount them on a "vent tree" as Brad has mentioned to get them some distance (inches) from and above the mains as this may prevent the vents getting clogged up with dirt etc. from the main. Using a vent tree as Brad also mentioned allows you to add or subtract vents to achieve the performance you desire.
  • Pin
    Pin Member Posts: 61

    According to the Brad White's first response to my post, Gorton #1 would vent all the air in the main in about 2 min and Gorton #2 would vent within half a min.

    If that is true, then what is the point of installing multiple Gorton #1 or #2 vents when the extra savings on time is insignificant? (ie. One Gorton #2 vents 30sec while two Gorton#2 vents 15 sec, and you need to pay double for the extra vent to save 15sec)

    I hope I am making sense. I want to find the best solution without spending too much time and money on installing extra vents if I don't have to.


  • Pin- You are correct! Brad is the man! Go with his suggestions. What I was saying was more addressed to venting capacities in general and I can now see where taken with the rest of this thread that might be confusing. Sorry I didn't mean to confuse the issue. I would suggest that you use a Gorton # 2 as my feeling is that having a bigger orifice, it is less likely to get clogged. On my old dirty steam system, my Gorton #1 has clogged up but so far my # 2s have remained working okay.
  • Brad White_202
    Brad White_202 Member Posts: 105

    Thanks Rod!

    I had not thought if #1's clogging more than a #2, but I defer to your experience. My "take" though is that a #2 has a 1/2" MPT end and the #1 has a 3/4" MPT end with a 1/2" FPT inside it. I suppose the inner guts are where it all happens so if you keep them protected, they would last (I hope!)

    I was suggesting multiple #1's in lieu of a single #2. As you noted there is a 3:1 venting advantage there. But fit is one thing, fine tuning another. That main would work well with a #2 if it fits, I agree. But if fitting (height) was an issue, multiples are just an option.

  • Brad-
    I need to qualify my statements. I really don't know if a Groton #`2 is less likely to clog up than a # 1.

    I'm just assuming that since I haven't had a clogging problem with the # 2s and since they have 3 times the venting capacity of a #1 that the larger venting orifices may be an advantage. I've saved the clogged #1s and when I get a clogged #2 will cut them both apart to satisfy my curiosity. I think your suggestion of trying to protect the vents by routing them up and back is a better`preventive measure against clogging rather than using a larger vent.
    Your idea of using a union on the vent tree is really good as it really simplifies servicing/installation of the vents

  • Pin
    Pin Member Posts: 61

    What are the differences between Gorton #2, Hoffman 75, Maid O Mist #1?

    Do they all work the same? Are there significant quality differences?

    Which is the best to go with?
  • the fastest vent ?????

    and the winner is an open pipe!!

    put a 3/4" ball valve where the present vent is, so that you can safely remove it, and time the point of steam arrival.
    i suspect you will see improvement. you will need someone AT THE VALVE to shut it off when steam arrives otherwise you could have a very damp surprise!
    when you know you need more effective venting, get the biggest ones you can find for each steam main, protected from water-hammer.

  • Venting Capacity-Main Vents:

    Gorton #1 and Maid of the Mist #1 about equal.
    Gorton #2 has 3 times the capacity as Gorton #1
    Hoffman 75 slightly less than half a Gorton #2

    This is based on info from Gerry & Steve's Venting Tables.
  • Pin
    Pin Member Posts: 61

    Could it be possible that the main vent is screwed on so tight that I can not take it off without a wrench?

    I tried to unscrew it by hand just like radiator air valves, but it wont budge.

    Is it okay to use a wrench and more force to get it off?

    Does anyone know what kind of main valve I currently have based on this poor quality pic?
  • Iwanttobelieve
    Iwanttobelieve Member Posts: 13

    i used a crescent wrench to take mine off when i replaced it a few weeks ago. It took quite a bit of work and time to get it to budge. i also used wd40 on it.
  • bob young
    bob young Member Posts: 2,177
    a 14

    you probably need a 14 " pipe wrench to unscrew that baby.
  • Might be an old Marsh

    but more importantly, it looks like it's screwed into a bushing. That's the hexagonal surface below the vent. The vent shank might be smaller than 1/2"- if that's the case, you'll have to get that bushing out of there and put in the right one.

    Since you only have the one main, use the Gorton #2. You can get them online at www.statesupply.com or www.pexsupply.com .

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Pin
    Pin Member Posts: 61

    I was able to get the old main vent off and look at it. The venting hole on top is so small. The hole is the same size as the size I put on my smallest radiator. Not sure why the previous owner put it in.

    After I got it off, I turned on the boiler to see how fast the steam travels through the main. However, I do not have a guideline to go by, so does anyone know how fast the steam normally travels with a good big vent?

    Also, can anyone tell me the dimensions for Gorton #1 and Gorton #2? I have 3 inches of space where the old vent was and I need to find out whether Gorton #1 or #2 will even fit in that tiny space or I need to make a bigger opening for it.

  • Brad White_204
    Brad White_204 Member Posts: 20
    Time and Dimension(s)

    Time? Just time it. That is as fast as it will be and is unique to your system, guidelines notwithstanding. Also the initial temperature of the pipe plays a large role as the metal warms up from dead-cold.

    Once warm and all things being equal, steam can travel 40, 50, 60 MPH or more. A typical range, depending on pressure, will be 3,000 to 6,000 feet per minute by my charts. Some systems, when warming, seem to take forever....

    The Gorton #1's will fit in the space you have. They are about 2 inches in diameter, probably less. The #2's are at least 5 if not 6 inches in diameter. Unless you can get into the joist space, you are looking at multiple #1's, I would think.
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