Main Vent Location

Miringanes

Hi, I have a house dating back to the 1920’s that has a one pipe steam system. Originally the boiler was oil but was converted to gas at some point before I bought the house. A year after I purchased I replaced the boiler.

I’m pretty confident that there is no main vent but the end of the main is above my finished basement ceiling so I can’t see anything. Further, I don’t hear any venting occurring from any of the areas that a main might be installed. I was able to get a camera above the ceiling and tried to snap some photos. There is something where the main (green arrow in first photo wrapped with duct tape) drops down to the return but it’s really difficult to tell what this is (red arrow in second photo). I need to get an endoscope to poke around and see what is happening above the ceiling. It MAYBE looks like a Ventrite but it’s possible my eyes are seeing what they want to see.

That being said, if I need to add a main, where would the best place be to do so without needing to open up gyp bd? I’m attaching photos of near boiler piping (third and fourth photo) balance of main that I can see from the utility room (photo 5) and return (white pipe running on top of cmu coursing photo 6 and 7). Im also attaching a plan diagram showing the main and its risers to the radiators. During a heating cycle, the return gets hot to the touch all the way from the drop to the boiler where it hits the Hartford loop. I’m not sure if this is from the condensation.

EBEBRATT-Ed

The vent belongs at the end of the main in the upper right hand corner of your dwg where it says 'DN".

I don't now can't tell from pictures. You can buy plastic access doors at HD you could cut one in the ceiling but it probably will not give you enough room to work through.

Someone may have raised the pipes when finishing the basement as well,

The other option if the first one is not accessible may be a vent on the pipe in the crawlspace feeding that rad or a large vent on the riser feeding that rad. Hard to tell without seeing it.

Miringanes

https://forum.heatinghelp.com/discussion/comment/1872189#Comment_1872189

There isn’t a vent within the crawlspace. That takeoff serves a single slim in wall radiator directly above the crawlspace in the kitchen. That radiator has a D vent on it.

I think trying to get to that drop to the return is going to require taking down a portion if not all the basement bathroom ceiling so I really want to avoid doing that, especially since I’d need to have some sort of access to maintain the vent if it should go.

EBEBRATT-Ed

Then if you think your short of venting you can put larger vents on any radiators that are near the end of the main.

But the best alternative to a main vent is to take the radiator valve off one of the rads and install a tee with a vent on the inlet to the radiator. Keep the radiator vent.

This is called a riser vent or a master vent.

RTW

As Eberbratt suggested, try "riser vent " option on inlet to radiator, it worked for me on radiator furthest from boiler. However, I did raise it on an antler about 6 inches high and also keep the radiator vent D on opposite side. If the rest of system is balanced, meaning vents nearest the boiler have smaller holes and those furthest have larger holes , you will notice the benefit

Regards,

RTW

mattmia2

That pipe about half way up the wall was probably below the water line with the old coal boiler which would have had a much higher water line. Now it is too low to treat it as a dry return and put the vent at the boiler but too high to be reliably filled with water.

You could go digging in the wall and find where that pipe drops down and thread it in place and put a tee in it although that would be a tight place to work in too but maybe not as bad as the ceiling where there seem to be several layers of framing in front of the vent.

Jamie Hall

That long white pipe halfway up the wall is NOT functioning as a return. Although it wasn't meant to do that, the new boiler water line is low enough that it is functioning as a steam main extension — and as a result, you can put a big main vent anywhere you want to along it and it will work just fine.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1872255#Comment_1872255

i thought it was closer to the water line but it is completely above the boiler so I agree yo could put a vent on there as long as the pitch is good. if there are any low spots collecting water you might get banging you didn't have before if you put the vent on that pipe.

Miringanes

https://forum.heatinghelp.com/discussion/comment/1872237#Comment_1872237

If you look at the first and second photos, I think that’s where there is a vent if I have one but it’s incredibly difficult to see. I think the thing I have the red arrow pointing at might be a ventrite at the location of the drop to the return but I’m not sure. I’ve been meaning to buy a scope and snake it in above the ceiling to see if I’m correct. Either way, I think that area is problematic because it’s buried within the bathroom. Unless I can do an elbow off of the drop tee then a 1-2 foot section of straight pipe and then a tee to a vent or multiple vents within the adjacent laundry area. I can draw up what I’m thinking in a little bit so it’s more clear.

Not my photo but a photo I found of a ventrite on a main which looks like it could be what the red arrow is pointing to, but like I said, need to confirm with a scope

This is a section sketch of what I’m thinking would need to happen if I do have a tee at the end of the main so that the vent would remain accessible. Everything on the bathroom side of the partition is inaccessible behind gwb.

Miringanes

https://forum.heatinghelp.com/discussion/comment/1872260#Comment_1872260

The white return is definitely above the waterline. Waterline on my boiler per the manual should be 23 7/16” or something like that, I’m getting the fraction wrong for sure.

The return is at least 36” aff and is pitched about 1/4” / foot for most of the horizontal run before it gets to the boiler room and pitches more significantly

EBEBRATT-Ed

As long as you keep the pressure low a vent on the horizontal should work. You have 13" to work with but if you get 1/2psi you will get water in a vent on the horizontal. Higher is better.

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1872335#Comment_1872335

Except that in a 1-pipe system the water level anywhere in the system never varies with the pressure of the system. Didn't you watch my video, @EBEBRATT-Ed ?

EBEBRATT-Ed

@ethicalpaul

Yes it's one of my favorites.