Getting a wye on a horizontal angled just right

[fcrick]

Hi there,

I've been putting some drain pipes and fittings together - the specific one I'm working on is a 3" pipe where I'm adding a 3" x 3" x 2" wye fitting that will go off to the lavatory. This pipe will also supply the vent for the toilet as a wet vent. The pipes are in soil under my basement slab, I've worked pretty hard so far to make sure the 3" run has a consistent slope that's exactly 1/4" per foot using a laser level as a reference. I have an 8" torpedo level, but it's a bit off and shows a slightly different bubble position if I just turn it around the other way, for example.

Especially since I'm working through a hole in the concrete, about a foot below, it's a challenge even when just dry fitting the wye to get the angle of it right so the pipe fitting coming off it will also have a 1/4" per foot slope. I know it doesn't have to be perfect, and if I'm reasonably close, I can just make sure the pipe, in this case a 4' long stretch, is sloped correctly, but the closer each step is to perfect, the more room I have for error elsewhere.

My strategy so far has been to dry fit it and get it as close as I can, and make a big pencil mark that goes across both the pipe and the fitting so I can line those up when I'm using solvent. This works only as well as I measure the angle, and while I haven't been way off, I'm always left feeling I could do a lot better.

I'm using ABS.

- What are some tips for getting the fitting's angle just right in this and similar situations?
- What's the best way to measure the slope of the little pipe coming out of the fitting?

 

[wwhitney]

When there's space available, I will firmly dry fit a stub of pipe into the wye branch inlet, so that I can measure the slope of the branch inlet by laying a torpedo level on top of the pipe stub. I favor this level, which has bumps on the face so that the bubble is centered at 2% slope, but you can also get torpedo level with multiple lines on the bubble for different slopes.

https://www.amazon.com/Redline-5-Five-Function-Level/dp/B071VPB17K

Then mark it for glue up, and double check the slope immediately after gluing. If it's off, sometimes I can quickly rotate it a bit more, but its very hard to make fine adjustments that way, as once you overcome the initial grab of the cement (if you can), you rotate it too much.

When there isn't space available, presumably it's because there will be another fitting very close to the branch inlet. So that requires another strategy. If, for example, you immediately hit a street 45, to end up parallel to the wye straight path (making an upright wye), then I would carefully preassemble the wye and street 45 to be planar (there are usually casting marks in the fittings that you can align). That way the 45 inlet will be guaranteed to be parallel to the wye straight path. The only variable then is the slope of the short diagonal segment between the parallel pipes; since that won't consume much height gain, you can usually just eyeball it at 5% or 10%, to be sure it is at least 2%.

Cheers, Wayne

 

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[Reach4]

I have an 8" torpedo level, but it's a bit off and shows a slightly different bubble position if I just turn it around the other way, for example.

Make your own marks. Both edges of the bubble. Turn level around. Mark both edges of the bubble.

So dead level would be when the edges of the bubble are between two pairs of your new lines.

 

[James Henry]

Craftsman makes a grade level. It is 12" long and it has hash marks on the bubble. Its what the pros use.