Ask Me Help Desk - Stack vent

I am installing a second kitchen in my basement and have a couple of questions about the vent. I can go up into the attic by making one 6' horizontal run and then straight up through two stories. I am then about 5 or 6 feet away from a horizontal run(sloping the opproprate 1/4 " per ft) that is feeding other plumbing to the main vent out through the roof. This horizontal run is about 8 feet awat from the vertical vent that vents to the outside through the roof. Can I tie into this horizontal vent, or will that be too far away from the main stack? The other possible option is this. I am also about 10 feet away from a different stack vent that I can tie into that starts right in the basement, but I am not sure it was done right to begin with. It runs straight up from the waste drain about 10 feet vertically(with a sink and shower vented into it along the way). It then takes a horizontal run about 20 feet before heading back vertically and out through the roof. The slope on the 20 foot horizontal run follows the 1/4 " per foot code. Is this a proper stack vent with such a long run? If so are either of the above mentioned options feasible for me to vent the new basement kitchen or do I have to run a new vent through the roof? Thanks for any help... I am tired of staring at this trying to figure it out and progress has stopped until I get it solved.

Hey Howie,

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I can go up into the attic by making one 6' horizontal run and then straight up through two stories. I am then about 5 or 6 feet away from a horizontal run(sloping the opproprate 1/4 " per ft) that is feeding other plumbing to the main vent out through the roof. This horizontal run is about 8 feet awat from the vertical vent that vents to the outside through the roof. Can I tie into this horizontal vent, or will that be too far away from the main stack?

If you maintain proper slope this will be acceptable.

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I am also about 10 feet away from a different stack vent that I can tie into that starts right in the basement,

You can not vent back into a stack vent where fixtures are draining above where you wish to revent.
Go with door Number#1 up in the attic. Good luck, Tom

So even though the sink that I am venting is (total) about 16-18 feet away from the main vent, I am still O.K. to vent into the stack that is about 11 feet away from the sink and 8 feet away from the main vent?

Also, on the second application that I listed, I would be tapping into the vent above any drains. The sink and shower that drains into this vent is in the basement and there is no other drains running into the vent from there. I appreciate your help. Just trying to make sure I have this right so I don't have to re do it. Thanks.

Let's get on the same page with terms.
Stack vent = A pipe through the roof that has fixtures discharging into it.
Vent stack= The part of a stack vent above the fixtures that goes thruogh the roof line. In other words a "dry vent".
Door number#2 just became doable. Looks like you have options.
Good luck, Tom

Thanks. Sorry about the terminology mix up. Your answers have been very helpful. I do have one more, however. Is an Air admittance valve a possible option. I ask because it sounds like a much easier option versus going through two floors or getting into the tiny area where the second option is. Here is the basic layout. I will run the drain for the sink out the side of the cabinet 5 ft and into a closet, make a 90 and run for 5 more feet, make another 90 and run 2 feet make a 90 and run14 feet into the stack.(I can use 45's instead of 90's for the second and third turn if this is more advisable... it is a utility closet so I can go at an angle to get to where I'm going if need be). The stack that it is draining into has 6 fixtures above it draining into it before it turns into a dry vent(kitchen sink, bathroom sink, tub, toilet, utility sink and wahing machine). Will a AAV work. If so where would you locate it(in the closet perhaps), and what size drain line would you use? Thanks for your help. I hope that was not too confusing.

I would go 2"on the drain and try to hold the 90's down to a minimum. I'm not all that comfortable with all those twists and turns but if I had to make a bend I would use sweeps or two 45's. Since I assume you haven't pulled a permit and the job won't be inspected then a AAV would work to vent the trap. Install the AAV close to the downstream side of the trap. Good luck, Tom

Thanks Tom. I appreciate your expert advise. I will take the 90's out and redirect using 45's and take a wider angle across the closet. You say to put the AAV close to the downstream side of the P trap. I see that the minimum distance away from the trap is 4" and the minimum height above is 6". And to use a Y instead of a san T. What is the maximum distance away from the P trap that it can be? I do want to keep within code. We are under the UPC and as I understand from all I have read it does allow one AAV per structure as long as at least one vent goes from the main outlet through the roof, unchanged in size. Am I correct on this. Again... thanks for your help and patience.

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What is the maximum distance away from the P trap that it can be? I do want to keep within code

UPC calls for the vent to be within 5' on a 2" drain.

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We are under the UPC and as I understand from all I have read it does allow one AAV per structure as long as at least one vent goes from the main outlet through the roof, unchanged in size. Am I correct on this

Milo or one of the West Coast plumbers can better answer this but as I read the code you're correct.

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And to use a Y instead of a san T.

A wye? To pick up the AAV. How about a san tee on its back?(see image) Milo, Lee, anybody anything to add? Regards, Tom