3 Inch PVC in a Half Wall?

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Hi, I'm going to build a non-load bearing half wall in the kitchen to create a peninnsula. The wall will conceal the water and electric for the sink cabinet.
I'm wondering what the maximum size schedule 40 PVC pipe is that I can run up through the floor plate of the half-wall. If I frame the wall using 2x4s, then a 3 inch PVC pipe will practically cut the plate in half. I'd prefer to avoid building the wall out of 2x6s, just to keep the wall size down. (I'm required to use a 3 inch pipe, but nothing was said about the wall thickness.)
I'm also going to put down 1/4 inch bc plywood underlayment over an existing vinyl floor. Should I put the underlayment down first, then build the wall, or put the wall right on the old flooring. (Don't want to pull up the old floor because of asbestos.)
Anyone have any input? Thanks
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Why do you need to run a 3" pipe, a sink and a dishwasher doesn't require more than 2".
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wrote:

Only your local inspector can tell you if he'll pass it, but since it's not a bearing wall, and not supporting a great load, you should be OK to run the 3". You'll have to put metal nail protector plates on the sides of the plate where the pipe comes up so you don't nail or screw through the pipe when you drywall or mount cabinets.
Can you just run the pipe up through the cabinet base instead?
IIWM, I'd do the underlayment first, then build the wall. Less cutting and fitting.
HTH,
Paul F.
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I already planned to use the nail plates, but thanks for the heads up. I thought about running the pipe up through the cabinet, but it's kind of a PITA to install the cabinet then, and it would be so much "cleaner" to have everything coming out of the wall. Perhaps I'm worrying too much?
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why 3" for anything except a toilet?
s

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S. Barker wrote:

Ah. I think "peninsula" is the clue. The 3" requirement is to permit air circulation and trap protection without having an actual vent to the outside.

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in

I'm not sure you understand the purpose of a vent. In your situation a 2" pipe with an air admittance valve would work better than what you're planning and be easier and cheaper to build.
There are two typical methods of venting an island/peninsula - this article covers both methods: http://www.rd.com/19540/article19540.html
R
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are not legal in my state.
As for a true vent, I would have to rip up two lathe and plaster walls, create three floor penetrations, and put a hole in the roof just to vent the sink. I have no access to the attic, so it would prove difficult to get the pipe through to the roof in the first place. I would also be required to re-plumb the entire house to be vented, as adding a vent would change the plumbing arrangement too much for "grandfathered" protection.
As it is, I'm merely moving the sink a few feet...much easier and cheaper! :)
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in

Cheater vent...yep, and I guess that GUI is a cheater interface. ;)

Maybe I'm not understanding you. You said your existing system is completely unvented. I got the impression that you weren't going through the inspection process. Maybe I'm wrong on that, but it's really odd that an inspector would insist that you conform to some ancient plumbing method so your house stays 'consistent' instead of doing what you can to upgrade it. Around here if you start messing around with the plumbing they'll make you add venting as required. If it's a lot of work - tough.
R
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the planning phase. As you say, if you mess around with the plumbing, they make you update it, even if it's a lot of work. However, merely moving a sink can be interpreted as not really messing with the plumbing. The bottom line is, if I don't want to re-plumb the entire house, I have to keep it as is. I'd probably put in an AAV if I wasn't going to sell the place. Thanks for your thoughts on this.
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I don't want to belabor the point...points, I'll be bringing up another one in a minute, but your code is behind the times regarding an AAV. It's not illegal, it simply doesn't conform to the existing code. Your whole plumbing _system_ doesn't conform to the current code! So what do you think you're really doing by sticking with 3" pipe? Please explain a single benefit of going with a 3" pipe.
The other point...there will be cabinets against this new knee wall, and freestanding cabinets don't need additional support, so why does attaching cabinets require stiffening the knee wall at all?
R
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Sounds fishy to me. A two inch with an air admittance valve should be plenty. Check the plumbing book. Or a plumbing friend.
s

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Internet, and the inspector. AAVs are not code legal in my state. As long as I'm really just /moving/ a sink, I don't have to re-plumb the entire house.
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I understand. One question though.... Is this new construction or what? Why are the inspectors involved on an inside the house operation?
s

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Think of it as two walls meeting where the 3" pipe is. Non-bearing it should be easy enough to do.

Any possibility of having to remove the underlayment in the future? If so, wall first, if no, should not matter.
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wrote in message

place. However, I'm getting cold feet. I should probably stick with a 2x6 wall to "do it right."

wall first. Future owners wouldn't appreciate having the underlayment sandwich if they decided to re-do the floor.
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shivermetimbers wrote:

non-load bearing the floor plate can be split.
When I have built half walls and I have access to them from the basement I place all-thread rods spaced at perhaps 2 ft intervals. I recess a nut and heavy washer into the header and pass the rod down through the floor plate and into the basement where another washer and nut allow me to tension the wall. This keeps the wall from loosening with time. I find that I can tighten up on the nut in the basement several times over the first couple of years as the wood dries. The top nut that is buried in the wall should be staked, or have Loktite applied so that it won't loosen up.
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to blocking in the adjacent wall, and the other end will go through the floor to blocking in the joists. It's an L-shaped wall, so it should be solid. It's also running perpendicular to the joists, so I will be able to nail the plate to the joists.
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If the knee wall is attached to the cabinets, where's it going?
R
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