How can I find (and test) my steam system main vent?

ethicalpaul

I said steam is more like air since they are both gases. Apology not accepted 😉

ARobertson13

Sorry, I read it twice because I thought it did not make sense. I read it a third time on my phone and realized I got it wrong. I have dyslexia.

ethicalpaul

I probably could have written it clearer, apology accepted 🙂

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810919#Comment_1810919

The concepts are making more sense.

Yes, A is full of air. You do not want steam to make the full round trip into A. The vent is at the end of the main. It is pointless extra steam reaching C that did not make it to the radiators. So, A blocks the steam and it mostly ends a B. Maybe some water hammer happens at A? But, A should be cooler than B/C. Once steam in B/C cools off, water drains into A, and the return into boiler?

CoachBoilermaker

Also, if the main vent is stuck closed, then B and maybe also C will not get hot, b/c the air inside A/B/C will not let steam pass. So, if B and C is cold, that means main vent is not opening?

If main vent is stuck open, then what happens? Steam reaches C, and then B, so both B & C get hot, and A will stay cold since all steam is escaping from B. But A stays cold when main vent correctly closes itself also. So what's the difference is B is open or closed? ie: Why does main vent at B need to close?

ethicalpaul

Your questions are very good

No water hammer at A unless incorrect near boiler piping exists. Typically only cold water that comes into contact with steam will cause hammer…so imagine C is improperly pitched and has a sag. In between heating cycles, that standing water will cool, and when steam comes across it, it may cause hammer (the steam rapidly collapses and the rush of air/steam to fill that void picks up the water and flings it against the pipe).

Yes, all condensate from the main and all radiators flows from C to A and continues down back to the boiler.

Any steam that condenses in C or B will cause a local area of low pressure that will allow more steam to fill it. People sometimes say "pulls in more steam" but really the steam is being pushed to fill the low pressure area…you can't pull steam.

Also, if the main vent is stuck closed, then B and maybe also C will not get hot, b/c the air inside A/B/C will not let steam pass. So, if B and C is cold, that means main vent is not opening?

Exactly. B and C staying cold is a key indicator the vent is failed closed. In that case, all the air of the main must escape through any working radiator vents, and that takes a long time, delaying heating.

If main vent is stuck open, then what happens? Steam reaches C, and then B, so both B & C get hot, and A will stay cold since all steam is escaping from B. But A stays cold when main vent correctly closes itself also. So what's the difference is B is open or closed? ie: Why does main vent at B need to close?

If B doesn't close, then you lose a lot of steam out of it, which means you will have to replenish the water in the boiler very much more often than you want. The introduction of fresh water into a boiler greatly increases corrosion of its iron. Preventing steam and water leaks is a prime maintenance item of any residential steam system.

I've brought your labels here to page 2:

CoachBoilermaker

Also, if main vent at B is stuck open, I will easily be able to see that hearing steam and/or seeing moisture dripping down riser B

ethicalpaul

maybe easy to see, maybe not.

Certainly easier to see when you cut away some of that sheetrock

CoachBoilermaker

@ethicalpaul I turned on the heat today. A & B & C were all hot. That's good, right?

ethicalpaul

Yes. I would expect A to not get as hot, or to take longer to get hot because it just gets hot from condensate, not from steam (if I understand your system correctly)

Steamhead

You're probably OK with that heat pattern. But that vent might still be too small.

Try this: measure each side of the basement wall. Say you find out each side is 20 feet. If the main wraps around the basement like I think it does, and there is a space of 2-3 feet or so between the main and the foundation wall, the distance of the main as it wraps around would be roughly 70 feet or so. A Gorton #1 is too small to fill that main quickly.

Another trick is to wait till the system is cold. Remove the main vent (you may have to unscrew the riser from the tee in the main to do this) and start the boiler. Use the stopwatch in your phone to time how long it takes between the time steam starts coming out of the boiler, and when it reaches the tee for the vent.

Now install a Gorton #2 in the tee. You will need a 3/4x1/2" bushing since this vent has a 1/2" thread. Wait till the system is cold and repeat the timing exercise. If the timing is the same or nearly so, you're done. If not, you need more venting. The #2 has its own short riser so you probably won't need to use the one you now have.

ethicalpaul

I like your advice, @Steamhead, but why would you test from cold when during the heating season and especially with insulated pipes, a maybe better test is with the pipes warm.

With the pipes cold, a much smaller vent will seem big enough because the steam will travel much slower since it has to heat the pipes much more.

It feels strange to argue against my usual position that massive venting isn't really that helpful.

Steamhead

@ethicalpaul , it's much easier to do it this way if you're not used to working with steam. There is no question when the steam has reached a certain point in the system when you start from cold.

Jamie Hall

He meant that air and steam are both gasses, which they are… all three are fluids (there are some remarrkably weird things which are fluids, by the way, technically speaking. But I don't think we need to go there?) Air is sufficiently far from it's condensing point to behave pretty much like an ideal gas. Steam, at the pressures and temperatures we play with, isn't — so it does some very odd things at times. But for most purposes it's a reasonably well behaved gas…

CoachBoilermaker

I reviewed this thread.

You guys think Gorton #1 because of thick nut on base of photo?

And you're suggesting it may not be the right size?

The main pipe in basement is basically a square of size 13x16 feet (about 58 feet of main)

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1814340#Comment_1814340

The main pipe in basement is basically a square of size 13x16 feet (about 58 feet of main)

I am not confident about removing the main vent. I have a pipe wrench and large channellocks.

I will turn on the heat and time how long it takes for ABC main vent area to heat up (after the boiler riser gets hot with steam). How long is correct vs. incorrect?

CoachBoilermaker

ethicalpaul

it’s not an absolute pass/fail.

As @Steamhead described earlier in this thread, it’s a comparison between steam filling your main with no vent vs steam filling your main with the vent in place.

Your vent is definitely a Gorton #1. The larger #2 is dramatically larger, almost comically larger

Steamhead

@CoachBoilermaker , as I said earlier, that main needs a bigger vent. I speak from experience. Go with a Gorton #2.

What size is the vent that is stuck? Could be 4, 5, 6, C or D.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1814509#Comment_1814509

What problem is the small vent causing?

Do you think the small main vent what's causing my radiators to not fill up?

Steamhead

https://forum.heatinghelp.com/discussion/comment/1814513#Comment_1814513

It is slowing the arrival of steam to the rads farther from the boiler.

You want the first minute or so of steam leaving the boiler to fill the main all the way to the vent. Then, when the vent closes, there is steam at every T joint where a radiator pipe connects to the main. So the steam rises to all the rads at about the same time.

This way, the boiler does not have to run as long to get heat to the house, improving comfort and saving fuel.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1814516#Comment_1814516

I will run the heat tomorrow

I will feel the boiler main riser and start the timer when it gets hot.

I will then listen for air at the main vent (gorton #1 in ceiling)

Then I will see how long it takes for the main vent ABC riser area to get hot.

Thank you for your time and expertise.

CoachBoilermaker

Did another test tonight.

The 60 foot main took 10 mins to heat all the way around. I followed the heat as it moved through the main. That was neat to feel the pipe heat up.

Here are the results of the radiator performance and vents:

35 mins after boiler turned on

BR #1
Never any vent sound
Only 3 or 4 sections are hot (total 8)

BR #2
Vent sound stopped
All sections hot (7 of 7)

BR #3
Vent sound still on
All sections hot (17 of 17)

LR
Never any vent sound
Slowly getting hotter (11 sections of 20 are hot)

DR
Vent sound still on
All sections hot (16 of 16)

Steamhead

Yup- you need a bigger main vent. 10 minutes is too long.

CoachBoilermaker

Can we review how to size out a main vent?

My main is about 60 feet long (big square in basement)

Main is 2.5" diameter.

It takes 10 mins from boiler start for heat to reach the end of the main.

It has Gorton #1 vent. Why do you think my system has a #1 vent?

When building the system, how would you spec out if you need Gorton #1 or #2 ?

CoachBoilermaker

To size out a steam main vent, we need to look at two main factors: the volume of air in the main that needs to be vented and the venting capacity of the vent itself. Here's a breakdown of how to calculate and determine whether a Gorton #1 or Gorton #2 is appropriate for your system.

1. Calculate the Volume of the Main Pipe

First, we calculate the volume of air inside the steam main that needs to be vented. For a 2.5" diameter pipe:

• Formula for Volume of a Cylinder (Pipe):Volume=π×r2×length\text{Volume} = \pi \times r^2 \times \text{length}Volume=π×r2×length
  • Radius rrr is half of the pipe diameter (2.5"/2 = 1.25 inches).
  • Convert length of the main from feet to inches (60 feet = 720 inches).

So, the volume (in cubic inches) of your 60-foot, 2.5" diameter pipe would be:

V=π×(1.25)2×720V = \pi \times (1.25)^2 \times 720V=π×(1.25)2×720

We can simplify this further or compute directly, but let’s move on to understanding the significance.

2. Convert to Cubic Feet of Air

Since vents are rated based on how much air they can vent, usually in cubic feet per minute (CFM), we need to convert cubic inches to cubic feet. There are 1,728 cubic inches in a cubic foot.

3. Determine the Venting Capacity

Now that you have the volume of air, compare it with the venting capacity of the Gorton vents.

• Gorton #1: Can vent approximately 0.33 cubic feet of air per minute at 1 ounce of pressure.
• Gorton #2: Can vent approximately 1.1 cubic feet of air per minute at 1 ounce of pressure.

4. Calculate the Venting Speed

From your description, it takes about 10 minutes for steam to reach the end of the main, which seems a bit slow for a 60-foot main. Ideally, the steam should reach the end in 3-5 minutes.

If the Gorton #1 is venting about 0.33 cubic feet of air per minute and it's taking too long, you can replace it with a Gorton #2, which vents significantly faster (more than 3x the speed).

5. Recommendations

For a 60-foot main with a 2.5" diameter, based on typical venting requirements and to reduce venting time, a Gorton #2 is likely the better choice. Here’s why:

• Volume Consideration: A long main like yours has a larger air volume, and the Gorton #1 might be undersized for quickly venting that volume. A Gorton #2’s faster venting capacity would more efficiently remove the air, allowing steam to fill the main faster.
• Time Target: A Gorton #2 would help reduce the venting time from 10 minutes closer to the ideal range of 3-5 minutes.

Next Steps

Switching to a Gorton #2 should improve the performance, but you could also consider adding more than one vent if space and configuration allow. Some systems benefit from additional venting capacity to ensure even steam distribution.

CoachBoilermaker

A friend has a spare Hoffman 75.

Should I grab that and try it on my main?

Anyone know the size of wrench for the Hoffman 75?

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1814695#Comment_1814695

@Steamhead

Just to be sure,

0:00 Boiler on

4:00 Main boiler riser to gets hot to the touch (steam being produced)

10:00 End of the main got hot

So, it really took 6 mins. for the end of main the get hot. (but 10 min from start of boiler)

Is that definitely too slow? Just want to make sure before I attempt this.

60 feel of main, 2.5" pipe diameter

delcrossv

Just do it. 😉

ethicalpaul

It’s not too long if you’re happy with it. Was that timed with warm pipes or cool ones?

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1816080#Comment_1816080

Cool pipes

ethicalpaul

Thanks. You might find it takes almost the same time to get steam to the main vent even with hot pipes, which would be a good indicator that you might benefit from the bigger vent. (Once the heating season kicks in fully you will be more often sending steam into already-warm pipes and that's when you'll want to move the air out faster)

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1816196#Comment_1816196

Sounds like there is little downside to going from #1 to #2. $150 vent

Main fear is either not being able to remove stuck nipple (then hire pro)

or breaking/cracking/stripping nipple somehow and having broken inoperable system.

Visions of plumber sawing the main and having to replace section, etc

ethicalpaul

I'm not a pro but I've now removed quite a few ancient pipes of different sizes. I've never had a 3/4" pipe that failed in those ways. It is too strong compared to the resistence given by its own rusted threads to collapse, break, or crack.

I have collapsed (made egg-shaped) a 2" pipe trying to get it out of an ancient fitting, but I was putting an immense amount of force on it (thanks to high leverage).

The main is going to be OK. As you apply the wrench, there is a way to do it where you maximize the twisting force vs the linear force. It's difficult to explain but you'll probably get it when you start to push on it…if the main starts to move much you're doing it wrong.

But if at any point you feel too nervous just put down the wrench and call a plumber or handier friend.

Be aware that 3/4" pipe will take a healthy amount of force to break free, you won't succeed by babying it.

delcrossv

Some penetraiting oil on the threads where the nipple enters the tee, wait a day,then a few taps on the side of the nipple with a hammer may expedite things.

Steady increasing pressure on the wrench and grip on the end to use all the leverage.

CoachBoilermaker

@ethicalpaul I could not even get the 24" pipe wrench to grab the pipe. I would tighten the clamps, and the wrench would just slip and spin. Tried facing the wrench both directions too. Wrench is heavy as hell to hold overhead also. Will try again tomorrow. I just put the wrench on the pipe straight on

ethicalpaul

You will face the opening of the jaws to the right (for loosening as you are doing), then put the jaws so they are swallowing the pipe (with the pipe against the back of the jaws), then adjust the wrench to close the jaws as much as you reasonably can, then rotate the wrench counter clockwise as viewed from above the wrench.

When you have the wrench in that orientation, it should close the jaws as you rotate it. Hold it tight against the pipe as your rotate it (but @Larry Weingarten says to leave some space so try that too). Put your left hand up the wrench nearer the jaws to hold them tight against the pipe and your left hand at the end of the handle to give good leverage. Once the pipe bites into the pipe you may move your left hand closer to your right hand if that helps. Don't let people tell you your cheap harbor freight wrench won't bite the pipe as well as an expensive wrench, it will work fine.

Stand on something solid to get better height if you need to so you're not holding it overhead where you leverage is bad

ethicalpaul

I should have added that the reason you hold the wrench with the jaws to the right when loosening is that the jaws are purposely created with a kind of "tilting" feature that appears as a "looseness" in the mechanism, and when it starts to "bite down" on the pipe, the mechanism will tighten down harder the harder you turn it.

But it's not automatic, you can't just hold the pipe in place around the pipe and start turning, you have to help the wrench start to bite the pipe. You have to put some muscle into it.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1816334#Comment_1816334

Not sure how to get it to bite. Muscle will just spin slide faster. Jaws do not grip pipe. Muscle makes no sense

neilc

you have the open of the jaws facing the same way you'll be pulling or pushing(rotating) the lever handle to, right?