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

CoachBoilermaker

Just moved. I'm trying to learn about my steam heat. Reading the Haloran book. He talks about clogged main vents or even guys replacing vent with a plug.

I have an old oil boiler. Finished basement. Pipes rise and go into the ceiling. How can I find (and test) my steam system main vent? How often does the basement finish have no clue about steam pipes and just covers the vents? How are they found when they get clogged? Thanks.

ethicalpaul

Finished basements are the worst. Your questions are good ones…lots of times the vents are closed off behind drywall.

Can you see any parts of your main(s)? (The mains are the big steam pipe(s) that run horizonally around your basement at the ceiling)

mattmia2

If the returns come from the far ends of the mains and the returns are above the water line, sometimes the main vents are at the boiler.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810249#Comment_1810249

Here is a video of my boiler

https://tinyurl.com/3frutcpb

mattmia2

You have a dry return. It should connect to the main somewhere out in the system and since I don't see a vent at the boiler, the vent should be there. Looking at where the radiators are and where that return is heading (the pipe that connects at the bottom of the boiler) or a thermal camera might help figure out where that is. That piping would be wrong for a modern boiler but is probably ok for that 50's or 60's boiler. You or a tech should flood it to make sure it isn't leaking above the water line.

That insulation on the flue should be removed, it is not designed for those temps.

JUGHNE

Your video is better than most we see from homeowners, however could you post still pictures of the boiler from all sides. Also show us the typical radiator that shows both ends of it.

Just an old guy here who likes to looks at still photos.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810307#Comment_1810307

Here is more video. There are no exposed pipes beyond what comes into the walled off boiler room

https://tinyurl.com/2p954fky

Steamhead

It looks to me like that main starts in the boiler room, loops around the basement and re-enters the boiler room where it drops into the return. The pipes look to be the same size as they leave and re-enter the boiler room.

Check the last riser off the main before it drops to the return. That looks like 3/4" pipe and I'll bet there is a main vent screwed into it, just above ceiling level.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810319#Comment_1810319

Need help decoding this.

Last riser off the main before it drops to the return?

A riser is a vertical pipe? The main is the horizontal pipe.

How can I find a riser if most of the main is hidden by walls/ceiling?

How can I find a main vent if its above ceiling level? Do I tear apart sheetrock just to learn about the steam system anatomy?

CoachBoilermaker

ethicalpaul

Last riser off the main before it drops to the return?

This use of “riser” means “pipe that goes from the main up to a radiator”

How to find it is why I dislike finished basements




Steamhead

@CoachBoilermaker , it's the last tee with a pipe going up into the ceiling before the main drops to the floor. You might be able to shine a light up in there, or you might have to make the opening a bit bigger.

JUGHNE

Any 3/4" pipe going straight up at the end of the main is most likely where a vent is or was.

3/4" is too small for a steam take off feeder in single pipe steam, so my guess is that is for the air vent.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810430#Comment_1810430

https://forum.heatinghelp.com/discussion/comment/1810430#Comment_1810430

I am having trouble understanding you. The last tee? What is the order? I have no idea what is first or last. The main drops to floor? Huh? I thought the main is in the ceiling. Can you tell me where to look in my video? Timestamp?

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810476#Comment_1810476

Where is the end of the main?

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1810595#Comment_1810595

First tee is closest to the boiler steam supply — it's the radiator supply that is reached first by the steam. Last is at the other side of the main (the end of it). It is reached last by the steam.

The main drops to the floor via a vertical pipe at some point to let the water return to the boiler, which presumably is near the floor. The picture you posted isn't really applicable.

From :17 to :21 in your second video you are looking from bottom to top of the vertical "drop" that marks the end of one of your mains.

Your video isn't that helpful, it's probably not your fault because so much is behind walls and ceilings. But the majority of your video seems to be aimed at sewage and water lines.

You might have a vent on this little riser, seen at :24 in your second video:

Here at :28 I believe is your last riser to a radiator, at least on this main. I can't tell if you have more than one main.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1810596#Comment_1810596

It goes by very quickly because you move the camera around so fast and so far- a common problem with these videos. But in the second video, you can see at 0:22, 1:59 and 2:23 where a 2" pipe elbows down at a 45° angle and reduces in size. That looks to me like the end of the main. From there, the pipe goes horizontal for a short distance, then drops and goes back into the boiler.

Now, at 0:23 in the second video, you can see a tee with a smallish pipe going up into the ceiling. At 1:25 you can see the same pipe coming up from the main toward a square hole in the ceiling, and a coupling screwed onto it. I bet your main vent is screwed into that coupling.

Having a steam main running around the perimeter of a basement is not uncommon at all. There is a neighborhood in Baltimore called Radnor-Winston where almost all the houses have this type of main.

JUGHNE

The end of the main would drop and connect into the bottom of the boiler.

It may drop to the floor and come up to a Tee called the Hartford Loop……or might just go into the lower tap on the boiler.

This is why still pictures are better than a video.

CoachBoilermaker

You guys are amazingly patient. Thanks.

Paul, I see the small riser at :24.

What am I looking for with the radiator riser at :28 ?

Steamhead

Don't worry about 0:28, he was just saying that's the last tee that actually serves a radiator.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810605#Comment_1810605

Got it. Thanks.

I'll take a closer look at the small riser at :25, near the end of the main.

CoachBoilermaker

When the heat is turned on, I should hear venting at that :24 small riser?

JUGHNE

Not if there is a plug in the pipe above the ceiling.

Many old vents were too small and plugged easily, as this may be the case.

Or it leaked and was capped.

Steamhead

Now, @CoachBoilermaker , next step is to measure the length of the main as it runs around the basement. I think the pipe size is 2-inch, the outside diameter would be a bit bigger than that.

dabrakeman

Yes, open this up and make it accessible.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810612#Comment_1810612

The house has 6 radiators. 3 on each floor. Will the basement main have 6 risers direct to each radiator, or does the top floor piggyback from the 1st floor ?

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810620#Comment_1810620

Just moved into the house this summer

The steam heat system is in good working order from what I was told.

So, I assume the vent should be working.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810629#Comment_1810629

Why do we want to know the total length of the main?

Not sure that's possible, as it's hidden in the ceiling anyway

ethicalpaul

 Will the basement main have 6 risers direct to each radiator

Typically one for each radiator yes

The steam heat system is in good working order from what I was told. So, I assume the vent should be working.

Bad assumption! and if they can't even see the vent, how can they report that it is in good working order?

Why do we want to know the total length of the main?
Not sure that's possible, as it's hidden in the ceiling anyway

By knowing the size and length of the main, you can get a good idea of the amount of main venting you should have. But really any is better than none. A lot better than none. But I'll bet you'll be told that a Gorton #2 is a good start.

When the heat is turned on, I should hear venting at that :24 small riser?

No, main vents are often too quiet to hear unless your ear is basically next to them…if they are even working as others indicated.

BobC

You can buy Inspection canmera's for $20 or so that have long 3/8" flexible probes and a screen that are designed to inspect inside of wall cavities and even piping. They have LED lighting so you can see what's inside dark places.

One of these would save a lot of work compared to tearing a ceiling apart.

Bob

CoachBoilermaker

It is starting to make sense now. That small riser at :24 must be the vent. What else would it be? Radiator risers are bigger. Plus, it's near the very end of the main.

Another thing I realized. There was an addition on this house. Added dining room and 2nd floor bedroom. They had to add risers to go to these 2 new radiators? I will look to see if there is a branch of main that goes under that side of the house.

Thanks to the guys in this thread. You are generous with your time, experience, and patience.

mattmia2

There could just be long runouts from the main to the radiators in the addition too depending on how everything is arranged.

CoachBoilermaker

There is a round copper thing at the top of the small riser at :24 !!

This is a main vent, right? Looks like a Gorton?

The nut seems flush with the sheetrock, so I'm not sure how you'd swap it out, can't fit a wrench there.

Could this mean the main vent predates the sheetrock?

ethicalpaul

Yes it looks like a Gorton #1. Yes it might pre-date the sheetrock.

You can tell if it's properly letting air pass by seeing if the pipe leading to it gets steam hot shortly after the main below it gets steam hot

Then you might be able tell if it's properly stopping steam by carefully reaching up there and seeing if it is letting hot steam out.

Alternately, you could put a pipe wrench on the 3/4" riser pipe and remove it. Then blow into the pipe with the vent upright. It should pass air. Then flip it upside down (vent at the bottom of the pipe) and blow into the pipe. The vent should block air.

Steamhead

Agreed- Gorton #1. Did you get a chance to measure the length of the main? if it's more than 20 feet or so, you'll want to upgrade.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810761#Comment_1810761

In other words, if air is passing correctly, what gets hot before what?

ethicalpaul

the C side first, heat should flow from the C side. You should be able to feel it travel along that main.

Then it should pretty quickly flow up B. Then the vent up there should close, allowing no steam to escape.

The A side should not get hot (at least not very far and not very hot), since there's no where for the steam to go after the vent on B closes.

ARobertson13

The only way to properly test any vent is to blow cold air through it in its operational position, then have steam go through at under 2 psi to see if it closes.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1810805#Comment_1810805

Not following the part about "A" staying cold.

Steam reaches C. Then goes up B. Main vent closes. Does B get "full"? Won't more steam from C now reach A since B is full of steam (and vent closed)? Or am I making the mistake of assuming steam flows like water? Does B not actually get "full", and then diverts new steam towards A since B is full? Doesn't work that way?

ethicalpaul

Steam reaches C, then goes up B, main vent closes. We are all good to this point.

Does B get full? Yes, B gets full of steam.

Won't more steam from C now reach A since B is full of steam (and vent closed)?

No because there is currently air in A all the way to the wet return/boiler where it ties in. The air won't let the steam go by. And the air will stay in there because there is nothing, no vent, to let it out.

The reason the air gets to C and then B is because the vent at the top of B is letting the air escape (that is the vent's whole reason to exist in fact).

Steam does flow kind of like water, but more like air since they are both gases. Steam flows from high pressure to low pressure, and at B there is high pressure so the steam won't flow there.

ARobertson13

Water and steam are not both gases, they are both fluids ( sorry for getting off topic)