I am in the middle of a kitchen remodel, where I am removing a wall between a kitchen and dining room. After removing the wall, I found a 2" PVC air vent that is venting the the drain for the sink. The air vent extends straight up and out the roof. My goal is to re-route this vent into an adjacent wall.

Pictures
1. Shows the drywall down with the vent
2. The 2x4s and air vent have been removed, new half wall was built and the far wall (with the pink stripe) is the wall where I plan to run the drain.
3. Closeup of air vent

Questions -
1. Is it required to pitch the air vent through the half wall or can I just run it horizontally?
2. Can I reduce the size of the vent to 1.5" if I'm short on space?
3. (best seen in picture 3) - the water supply pipe extends a few inches to prevent the pipes from banging, can I afford to reduce the size of this my a few inches? I'd like to the vent in the center of the wall.

Thank you for your help.

Hello Thomacy...

I would pipe this so it runs PITCHED at about 1/8" to 1/4" pitch per foot toward the drain. I would run this so that you offset the vent under the counter with a 45 degree fitting and run into the 2nd stud bay with your vent (see picture)... then pipe up as drawn in red below.

You can reduce the vent to 1.5" if it makes it easier...this is legal everywhere that I know of. You will need to increase back to 2" at the vent pipe that penetrates the roof.

I did not understand question about the water pipes?

Let me know...

MARK

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Originally Posted by thomacy

<snip> The air vent extends straight up and out the roof. My goal is to re-route this vent into an adjacent wall.
<snip>
Questions -
1. Is it required to pitch the air vent through the half wall or can I just run it horizontally?

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If you are certain that there is no drain above, you could get by with minimal slope, just don't go below level anywhere, but I would get any slope I could up to 1/8 in/ft.

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2. Can I reduce the size of the vent to 1.5" if I'm short on space?

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No. Besides, there's a good chance that it is venting more than just the kitchen drain.

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3. the water supply pipe extends a few inches to prevent the pipes from banging, can I afford to reduce the size of this a few inches? <snip>

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Yes, you can cut them down. After a year or so there's no air left in there anyway. If you want something that will work longer term, get a new hammer arrestor and install that above the tee. They are only about 4 inches long.

You also could build an "island vent". Short description: Run the vent pipe as high as possible in the wall and then turn it back down (3 elbows, 45-90-45) and go below the floor and laterally to where you can get to the vent stack. Look it up in one of the DIY plumbing books at your local library (or bookstore :) ). Pictures are better than words and I have skipped some of the details on cleanouts and cross connections to the drain lines.


Just read mass plumber's answer. Interesting on reducing the vent size, we aren't allowed to do that here. His answer is good though and reducing size sure would make life easier!

There is a need for some slope in a vent since most vents are open to the outside air. Rain can go down the vent and its not an isue if there is slope. I am not allowed to reduce vent stacks anywhere but codes do vary. I observed many things from your pictures. #1 wine glass is empty, refill it. 2. air chambers are a bit tall but why do you need to reduce.

Thanks for all your quick help. I'm a computer tech, so, I went and helped out a few others :)

I'm going to run this at a pitch through the half wall.

Mass - just a question about the 45 degree fitting? I attached another picture with a better idea of what I meant in question 3. Based on the other posts, it sounds like I can reduce the size of the copper pipe to give me more room to run the vent.

Thanks again.

Yes on both counts. The air chamber is twice as tall as need so if you must cut it shorter.

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2. Can I reduce the size of the vent to 1.5" if I'm short on space?
No. Besides, there's a good chance that it is venting more than just the kitchen drain.

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Here I disagree. Name me just one instance where a kitchen vent will vent more then the sink. While my inspecter doesn't like 1 1/2" vents my code book tells me it's a legal vent for up to 8 fixture units. Good luck, Tom

Hey Thomacy...

Like Tom said, reducing vent to 1.5" will be fine. The big deal in reducing only comes when penetrating the roof as this must be at a minimum 2" pipe...and you already have that in place.

Vents require 1/8" pitch at a minimum in my code book, but I don't think it is a big deal if you don't here, just be sure you're not back-pitched.

The copper pipes can be cut down... no problem! But, like Ballenger suggested, you don't really need to. There is plenty of room above these pipes to drill holes across the half-wall and install the vent.

Finally, if you look at the drawing I posted earlier you will see a slight KINK in the red line as it heads toward the wall. Here, I planned on you using a 45 degree fitting to enter into the cabinet space a bit and then into that 2nd stud bay of the full-wall and run up the wall. If you don't offset into the cabinet where I am suggesting then you will end up in the third stud bay of the full-wall where there is a 2"x4" stud that will not allow you to put a vent in there anyway..? That make sense?

Let me know if that was clearer...

Happy Thanksgiving...

MARK

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Originally Posted by speedball1

Here I disagree. Name me just one instance where a kitchen vent will vent more then the sink. While my inspecter doesn't like 1 1/2" vents my code book tells me it's a legal vent for upto 8 fixture units. Good luck, Tom

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OK, "good chance" was a poor choice of words. Where we are, there are plenty of basement laundries and other basement plumbing though.

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Name me just one instance where a kitchen vent will vent more then the sink. Where we are, there are plenty of basement laundries and other basement plumbing though.

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We have laundry and sink branches connected aLso. But we aren't talking about drainage are we? We're talking about vents and Every fixture that has a trap must have it's own vent. No Miller, A kitchen vent will vent just one fixture, the sink. That's not to say another vent may revent back into the kitchen vent. But the kitchen vent vents the sink and that's all. If you have knowledge otherwise now would be a dandy time to produce it. Regards, Tom

Hi all...

I see a problem in the full-wall that I missed earlier... solid EMT conduit!

Thomacy, if that conduit cannot be repiped with a flexible BX cable (armored flexible cable) then you may need to install an air admittance valve (an AAV... sold at all home supply stores.) in the half-wall or under the sink.

Here, the AAV is installed so it above the trap. It must be accessible for the future as these can fail over time and need to be replaced (install access panel or bring the AAV under the cabinet/sink as in the picture below). Be clear, however, that these may not be LEGAL in your area and if that is the case this may not be an option for you (call a local plumbing inspector and ask him if they are allowed).

Check this all out and let us know what you think...

MARK

We are rerouting that conduit, as well, so, it will run around the PVC vent.

I'm going to pitch this through the half wall.

The AAV is an interesting idea, but, I'm not going to be able to get into the wall once the kitchen is finished and would rather install a more permanent solution.

Do not install an AAV inside a wall that will be closed, they evntually need servicing.

Wow, finally can say my UPC book is less restrictive. My code says you can run a vent level or sloped (however I do recommend at least minimal slope). I agree that you will be able to reduce ks vent to 1 1/2. I see no need to shorten water pipes. I would actually say the higher you can keep your vent the better. Use 90s(its just a vent, no worry about restriction). I think your red line view will work just great. Just do the best you can with the space you have and you will be fine. Good luck and let us know how you enjoy your knew kitchen.

Hey Thomacy:

Great job... glad to hear about the conduit being re-routed and glad to hear you are looking for a "more permanent solution" here... :)

You should be all set now!


Thank you for the update.

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Originally Posted by speedball1

We have laundry and sink branches connected aLso. But we aren't talking about drainage are we? We're talking about vents and Every fixture that has a trap must have it's own vent. No Miller, A kitchen vent will vent just one fixture, the sink. That's not to say another vent may revent back into the kitchen vent. But the kitchen vent vents the sink and that's all. If you have knowledge otherwise now would be a dandy time to produce it. Regards, Tom

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Sorry, I've been gone and haven't been able to keep up with this thread. As to your reply about my being incorrect. Don't you ever see a "wet vent"? Where the drain line for a fixture directly above acts as the vent for a fixture on the floor below? I do mainly repair and some remodel work and admit to having to go to the code book to get questions answered, but I see this all the time and I've gotten it inspected in remodel work in the past. If the example shown in the photos above has a basement laundry below it, good chance that's a wet vent. Especially seeing the 2" line for just the sink.

EPM

1 1/2 should still be adaquate for fixtures involved, unless toilet vent is involved. Im not allowed to wet vent kitchen sink, or use a vent as a drain for kitchen sink in my area. I do see a lot of it, and it works just fine, but as far as new install, not allowed(here). Most fixures may be wet vented, but usually not kitchen sinks or washing machine drains.

Great back and forth here. Interested to hear input from all. Take care.

Here's the final result (not to bad for a computer tech, huh?)... Mission accomplished! Thanks to all for the suggestions.

Meticulously piped! Nice job.

EPMILLER...

Speedball is down for a few days, but I wanted to quickly respond to your post on WET VENTING. You said, "Where the drain line for a fixture directly above acts as the vent for a fixture on the floor below". The only way a vent acts as a vent for a fixture on another floor is if you tie the vent from the lower floor into the vent at least 6 inches higher than the flood level rim of the tallest fixture on the higher floor... and then it's not a wet vent, but just a vent.

In fact, if you look at the pictures above and you add a sink from the basement and call this kitchen sink a WET VENT for the basement sink... AND THE VENT FROM THE BASEMENT DOES NOT CONNECT INTO THE KITCHEN SINK VENT AT LEAST 6 INCHES ABOVE THE FLOOD LEVEL RIM OF THE KITCHEN SINK... you will not have a wet vent but a major SIPHON ACTION as the kitchen sink drains past the basement sink and the basement sink is left with NO VENT and therefore basement sink bubbles and water can be siphoned from the trap... a major health issue from a plumber's perspective!

This is exactly the mistake that so many homewoners make... connecting into a kitchen sink drain coming into basement and then not adding a separate vent for the basement sink.

Further, kitchen sink, garbage disposal, dishwasher and washing machine drain pipes CANNOT act as wet vents for any fixture... not in any code book I know of.

So, look at wet venting again... let me know what you think.

Good day...

MARK

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Originally Posted by thomacy

Here's the final result (not to bad for a computer tech, huh?) .... Mission accomplished! Thanks to all for the suggestions.

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This looks great. I would offer a little advice to any other onlookers at this sight that see this piping. You had plenty of room to move the vent up to the top of the studs. I would have drilled the studs as high as possible( while still having room for minimal slope). Don't worry, you will be just fine with your install. Just my thoughts on things.

The only reason I point this out is this... now you have a length of horizontal vent below the floodrim of the fixture which it serves. Not really a problem as far as I'm concerned.

Do make sure you either install stud guards, or measure and mark sheetrock so you don't end up drilling a screw into pipe while sheetrocking. Wish you a speedy project, and have a merry christmas and happy new year.