I am struggling with a math/geometry problem with a wet vent rough-in:



So under the sand there I have a 3”x2” wye “rolled” on it’s back at 45 degrees.

You can see the 2” stub coming up and out. I now need to “turn” this stubout “flat”/horizontal, then run it straightish, and then I am planning on using a long-turn 90 to turn it vertical inside the future studded wall. It will then rise vertically to the bottom of a sani-tee, with the lav dumping in the side and a dry vent off the top.
(In the photo, you are looking head-on at the future toilet, and the lav will be to the left of the toilet against the same wall)

My issue is turning this stub horizontal. I fit a 45 elbow on it but that would actually turn it downwards. I was wondering how to do this one.

This is like one of those mitred crown molding cuts. To make the two pieces meet at 90 degrees you have to give each a crazy angle because the board itself is angled.

not much to say except you need a few fittings and a short piece of pipe to play around with.
we all go thru this. it becomes a game of trial and error.
possibly three 22's would not be too restrictive for the flow but would still give you enough play to get the angle you want.
option 2.. sometimes you just take the angle you have and put a fitting on it to face it straight up and then use a long sweep 90 to aim at your desired location.

palm329, I think I know what happened. You rolled the wye fitting "axis" up 45 degrees, thinking that by doing so the branch will be off horizontal by 45 degrees. That is not the case unless the branch is perpendicular to the fitting axis (such as a combo). Bear in mind the branch of the wye itself is already 45 degrees off the fitting horizontally, and when you rotate the fitting 45 degrees, that branch itself comes up about 35 degrees along the 45 line. Check that with a short torpedo level.

If you are indeed about 10 degrees off, one thing you can try is to get a 30 degree elbow, which will send you off by just 5 degrees up which depending on the length PVC pipe can flex a little bit to the 1/4" per foot you need. Another option is to get a 60 degree elbow to put on that branch and that will take you back to horizontal BUT it will end up being 90 degrees or parallel to the fitting, so you have to put on another 45 to get it to where you need it to go. Or use several small angle fittings to fudge it.

It is running at a 45 degree slope... depending on the angle you’re measuring it from.

For example, I can use the 45 elbow to turn the pipe “flat”, however only if I want it headed either parallel to the 3” pipe below, or perpendicular to it. I cannot use the 45 degree to continue the pipe on its current heading...

For simplicity, I will probably have to turn it parallel, then use a 45 or a 22 to hook it over to the left towards the vanity wall. Then turn it straight up using the LT90. I will post a photo if I can pull this off.

PS - lesson learned, next time I’ll rotate that wye only to the proper angle so that once a regular 45 is on the end, it will end up flat!!



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If you want to attach a 45 degree elbow onto that pipe currently capped with a rubber fernco and have it be flat heading in the same direction, then that fittung has to be rotated such that the branch is 45 degrees ALONG ITS OWN AXIS, which is different from rotating the fitting itself 45 degrees off horizontal.

Rotating the fitting 45 degrees off horizontal will get you a branch only 35 degrees off vertical.

On the other hand, in order to get a branch to be 45 degrees off it's own axis, you have to turn the fitting 63.6 degrees, according to my calculations.

A 60 degree, 1/6 bend, will roll you up 45 degrees, 90 degrees to the toilet line, and then you can use a 45 to come up in the wall.