Main Vent Sizing

Orple

Based on what I read in Holohan's texts and on the Wall here, I think I've calculated my main vent sizing correctly, but figured I'd submit it to the voices of experience to make sure that I'm not doing it wrong.



Currently, my system only has one main clogged main vent that I need to replace. It is located at the end of the condensate return of the only main line (main line is 16' long @ 2" and condensate return is 15' long @ 1") . My calculations are that I need to clear .5 cubic feet of air from these pipes, along with an additional .25 or so for the boiler piping for a total of .75. At 2 ounces of pressure (which is what I'm shooting for), I believe that two Gorton #1's should be able to clear that.



That sound right to you folks?

BobC

That should be fine

You can never have too much main venting but you also don't usually have enough money to use a single big vent, the two #1's should be fine. Try to come up and then over a foot or so with the vents and then get them as high as you can. Make sure any horizontal run has just a bit of pitch so condensate can find it's way back to the boiler.



Bob

Orple

Piping the vents

Thanks for the feedback, Bob. I bought a set of Gorton 1's today, which should be here in a day or so. So now I need to think about how to pipe them. My plan right now is to run as long a nipple as I can from where the vent is seated now (see pic), and into the bull of a tee. From each end of the tee, I'll run a nipple, an elbow, and then the vent. Ultimately, it will make a U shape sitting above the rising nipple (or a Y if you include the rising nipple).



Two remaining questions I have:



1. How do I keep a pitch on both horizontal nipples? I could use a series of 45 degree elbows and run one line off the bull of the tee, but I imagine there is a more elegant solution.



2. I think the current main vent is in a bad spot (after the condensate drop to the equalizer). Again, see the picture attached. It looks like a great way to feed water into the vents. But, if there is a way to make it work, it would be an easy replacement.



As a possible alternative, there is a tee with a cap on it about a foot before the main vent; one thought is to try to get that cap off and put an elbow with a bushing there and run the vents off of that. But I think that's only a marginally better solution entailing a good bit more work and risk. But the union that is right before it will make the whole job a bit easier.



The right thing to do is probably to take out the pipe in between the two tees (the one with the current vent and the capped off one) and install a new tee before the return with the bull facing up. If it is the right way to go and worth the effort, I'll do it, but I figure always better to ask firs than rush in to do the wrong thing and/or unnecessary work.

Orple

Height of the main vents

Based on a comment from Hap_hazzard on a separate post, I'm thinking through how to raise the vent as high as possible above the main as well. I'm guessing I'll want to knock out some of the cement board that was tacked to the ceiling to get another 8 inches or so.

BobC

similar situation

My piping is similar to yours and I lost a vent because of what I suspect was a slug of water slamming into it. I came off the vent mounting spot with a short nipple and a 90, I then used a long nipple - and a T (with a vent on it) - another  nipple and a 90 to a second vent. They are both up in a joist bay, I'm using a Gorton #1 and a Maid O Mist #1 on my setup. You could use a T at the last spot so you could add a 3rd vent but I don't think you'll need it.



A lot of the fittings you buy at the local hardware store are not very precise but that works out in our favor because we can use that to help us get a little slope back to the main so water will drain. I left my vent assembly uninsulated so they would be the last to heat up and thus keep the vents open a bit longer.



Bob

Orple

Further considerations

Bob, I take it that the long nipple was to get you into the rafter space? Or did the length also help limit water intake?



I take it you figure I'll be in reasonable shape building off where the vent is now? I'm concerned that, being a straight shot from the condensate return, it will tend to be the path of least resistance for the water. If the water was moving fast, I wonder if it would follow the dropdown or keep going straight.

BobC

use a level

Because fittings (especially the imports) are often not threaded perfectly square you should use a level to find the orientation that will allow for some slope back to the boiler. I could not go back along the main in my case because there was a 6X8 beam in the way, I was able to find a good position using a level.



The length of the horizontal nipple will shield the vent from any damage caused by a slug of water.



Bob

SWEI

Can you fit a third tee

between the two tees in photo #2?

Orple

I was thinking about that

I imagine it would be less prone to water slugs, doing it that way. It's just a little more work. If I did that, I'd probably just use the tee that feeds the vent right now and replace it will an ell, and use that tee in the middle.

Orple

Delay

Well, I'm having no luck getting any of the fittings apart. The main vent looks to be rusted to the bushing, and the bushing is rusted to all getout (I wonder if it isn't black pipe, because it rusted much more than the ell below it). None of the fittings from the vent to the tee want to budge (see pic 1)



So I started on the union a litter further back (see pic 2), and still no luck. Granted, I'm only working with a 1.5' and a 1' pipe wrench, so I think it's time to go buy either a larger pipe wrench or a set of cheater bars.



I'm just surprised they're this stuck. It looks like only old dried pipe dope on the threads, although it looks to have been a long while since they were put in. I've tried soaking them in WD40 and unsettling them a little with a hammer, all to no avail. I can put a little more muscle into it yet, but would rather have the control (and not smashed fingers) that I can get from longer handles.



Any thoughts?

BobC

Cement

Some pipe dope becomes like cement after a few years and it can be a bear to break free. Once that stuff sets, penetrating oil is useless.



You will need an extension on your wrench, I remember using an 18" wrench on mine and it took a couple of good heaves to break the vent free. When I put up my new piping and vents I used teflon tape so it will come apart real easy if I have to go back in there.



Bob

[Deleted User]

I'm no expert,

but my plumber uses a propane torch on pesky old pipe fittings. That seems to soften them up.

Orple

Delay

Looks like it's gonna have to wait until after the holidays. We have a good bit of travel to do, so I'm going to wait until I have the time/space to do it right and keep an eye on the results. I'll pick this up again right after the new year.

Hap_Hazzard

Heat

The trick to it is that pipes and fittings expand at a rate roughly proportional to their circumference. If you can focus your flame and apply the heat mainly to the outermost component, and heat it quickly, that will loosen it up considerably. I don't think it softens the thread sealant, but it probably breaks it loose.



Don't try this on boiler tappings, by the way. The boiler casting will not expand locally, and if it did it would probably make the joint tighter--and crack the casting. If anything you'll just get the nipple hot and expand it, making the joint even tighter.