Increasing the slope of a drain from level copper to sloped PVC

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As to the holes, if the pipe will fit, that's fine. But if you are only testing the holes one at a time, you may find out they are not aligned in the dimension perpendicular to the wall.

If you can drill your new 2" holes accurately enough, it will work, but it's hard to be that accurate. You could make a guide fixture to ensure your new holes are the same distance from the front edge of each stud, and then find out those front edges aren't actually all in plane with each other.

So 2-1/8" is a practical minimum.

Cheers, Wayne
The holes seem pretty uniform in their distances from the front edges of the studs. And I find that a 1.5" PVC pipe wollers around in them pretty good, except for in the king stud. [edited: I mistakenly referred to jack stud.]

I'm not shoving a long pipe through the holes from one end. I'm putting a PVC coupling between each pair of studs, to join several 14"-or-so sections of pipe. Will the PVC couplings be forgiving enough to handle some slight zigzagging without leakage or other ill effects?
 
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wwhitney

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Will the PVC couplings be forgiving enough to handle some slight zigzagging without leakage or other ill effects?
Probably? Just like the Fernco or Mission banded coupling will probably accommodate 1 degree of bend if necessary? PVC is inexpensive, so it doesn't hurt to try it, if you can get the pipe fully seated in the coupling with adequate solvent cement, it shouldn't leak.

Cheers, Wayne
 

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Probably? Just like the Fernco or Mission banded coupling will probably accommodate 1 degree of bend if necessary? PVC is inexpensive, so it doesn't hurt to try it, if you can get the pipe fully seated in the coupling with adequate solvent cement, it shouldn't leak.

Cheers, Wayne
Okay, between the banded coupling and some slightly crooked joints, I guess I can get enough slope. Really I don't know why there doesn't seem to be such a thing as a 1.2-degree elbow.
 
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Reach4

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I wouldn't expect the couplings to bend, just that the pipe could go into the coupling a little out of line and yet not leak.
Sounds like a bad idea to me. In the store, maybe find a pipe with a set to it.

Packing a section of pipe with sand, heating, and bending is a much better idea. Try this google search: bending pvc pipe with sand
 
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Is there a code requirement for slope in drains? Both this kitchen-sink drain line and one of the bathroom-sink drain lines have zero slope. I can see that zero-slope is bad for copper, but what about PVC?
 

wwhitney

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1/4" per foot minimum slope for drains under 3" in diameter. 1/8" per foot minimum slope for 4" and larger. IPC and UPC disagree on 3" diameter: IPC allows 1/8" per foot, but UPC requires 1/4" per foot.

Cheers, Wayne
 
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I'm close to finishing this job, which includes replacing the sink traps. Is the slope of a P trap horizontal section also supposed to be 1/4" per foot? I am not seeing how to give it slope when the sink tail pipe is vertical.
 

wwhitney

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Is the slope of a P trap horizontal section also supposed to be 1/4" per foot? I am not seeing how to give it slope when the sink tail pipe is vertical.
The slope of the inch of elbow after the p-trap u-bend is what it is. But from there to the san-tee (or other vent) the trap arm needs to be sloped 1/4" per foot.

Cheers, Wayne
 

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I'm close to finishing this job, which includes replacing the sink traps. Is the slope of a P trap horizontal section also supposed to be 1/4" per foot? I am not seeing how to give it slope when the sink tail pipe is vertical.
Are you talking about a slip joint trap? You can raise and lower the connection to the tail piece within limits. If you cannot raise the connection a bit, cut a bit off of the tailpiece.
 
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A picture would help. Sounds like a load bearing wall, so some reinforcement is likely in order.

Cheers, Wayne
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Sorry for the delayed response. I had a couple other dragons to slay. I've mostly wrapped up this drain replacement. Here I'll try to tie up a few loose ends.

We used a 2" hole saw to vertically enlarge most of the holes that needed to be vertically enlarged. The existing holes were 2". We positioned the hole saw by fastening a sheet of 1/4" plywood (with a 2" hole already cut through it) to each stud as we enlarged it. I'll be installing some stud shoes for reinforcement.

One of the studs had neighboring studs too near, so that there wasn't room to accommodate a power drill. So we couldn't use the hole saw to vertically enlarge the hole through that stud. Instead we used an oscillating saw (multi-tool) to make a squarish enlargement.

I was wrong when I said one of the 2x4's of the king stud was cut off. There is a jack stud nailed to the king stud. So the drain pipe was passing through three 2x4's nailed together in one place. I've attached a picture with the camera resting on or near the sill plate. The pipe shown is a water pipe, not the drain pipe (which is higher up). After taking the picture, we cut maybe 6" off the bottom of the jack stud, so that the drain pipe only had to go through two 2x4s. We put a couple new nails through the remaining part of the jack stud for reinforcement. [edit: I'm still not sure I'm using the term 'jack stud' correctly. Anyway there were three 2x4's nailed together, and one of them did not go all the way down to the sill plate.]

We did use Fernco rubber couplings to join copper to PVC (for both the drain and the vent). Picture attached.

Thanks for all the help and the replies. The key decisions were to 1) replace the bad 1-1/2" copper with 1-1/2" PVC while giving a standard 1:48 slope to the new PVC, 2) use the flexible couplings to join new PVC to remaining good copper, 3) use a plywood guide to position the hole saw to raise the tops of the holes through the studs, 4) use the oscillating saw (multi-tool) on the studs that the hole saw couldn't reach, and 5) use stud shoes to reinforce the studs at the sites of the enlarged holes.
 
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