I ran a short (18" long) section of 2" drain pipe from an existing wye to a new 2" shower drain.

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I sloped the drain pipe correctly, but failed on eyeballing the plumbness of the p-trap and riser. Consequently, the shower flange is off 5/16" from side to side.

I plan to cut a coupling into the riser and hopefully there will be enough play in the joints to straighten out the flange. To maximize joint play, I will apply primer 3 or 4 times to really soften the pvc. I will lay a torpedo level, on it's side, on top of the shower flange while I am installing it, so I can check level in two directions at once. Sounds like a good plan??

In the future, is there a better way to install pvc pipe level and plumb? Two methods I've heard...

1. Dry fit parts, mark fittings and pipe with a sharpie, and glue back together. Downside, pipe doesn't fully insert while dry. And, I had trouble accurately realigning the sharpie marks.
2. Attach torpedo level to pipe while gluing. Downside, you can only check plumbness in one direction on a riser unless you take the time to perfectly cut the pipe end square, then you can lay (and attach securely somehow) the level on its side on top of the pipe end. I guess I could have done this with the p-trap...maybe tape a level onto the top of the p-trap hub.

By the way, I heard plumbers run the last few feet of pipe before a p-trap level, without slope, so the p-trap is level too. Is that true?

I could use a Fernco or a pair of 1/16 bends (22.5 elbows), but seems like overkill...kinda like my writing about it instead of just doing it.

I am assuming a p-trap will still work fine even if it's not level, but sloped a little like the drain pipe...1/4" to 1/2" per foot.

Thanks a bunch!

Cut the horizontal pipe near the wye. A coupling that far back will allow a lot of adjustment at the flange with little misalignment at the coupling.

Thank you for responding, Steve.

The horizontal pipe has a reasonable slope...around 1/4" per foot. The vertical riser also leans in that same direction, but with a little more slope.

So, if I put a coupling in the horizontal pipe, and rotate down, I may lose all the slope in my horizontal pipe before the shower drain levels enough. That's why I was thinking of putting the coupling in the riser.

Nick



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nicholas, you NEVER slope or pitch a trap. it is always installed level even if the last foot or so of drain is also level.
what i would do in your situation is cut a piece if strapping long enough to wedge the riser back so it goes slightly past plumb the other direction. leave it overnight and in the morning when you remove the stick the pipe should be plumb. a little sideways force on the pipe will do no harm.

Hello Packy.

I am surprised that a p-trap would be that sensitive to level. I would think a little slope, like that of a typical drain...1/4" per foot...would be acceptable. I wish I had a p-trap with me. I imagine if you fill the trap with water and tip it a little, hardly any water would spill out. So wouldn't the seal still be okay? Not meaning to be disrespectful. Just trying to learn.

I did read somewhere that a trap might siphon easier if not level. It didn't say how far out of level.

By the way, the other day, I was speaking with a Charlotte Pipe rep and he said the same thing you did...Most plumbers will force the riser pipe/flange into position. I was shocked because I always heard to be gentle with the pipe and don't stress it.

Nick

"...By the way, I heard plumbers run the last few feet of pipe before a p-trap level, without slope, so the p-trap is level too. Is that true?..."

Instead of running our horizontal drain pipe directly to the vertical drain, we'll target slightly to the left or right of vertical. Then, when we are within a foot or less of vertical, we'll throw a 45* (or 22, or 60) into the horizontal right before the trap and set it flat. That way, we maintain pitch to within a foot or so of the trap.

Beautiful M & M! That makes sense and seems easier and more foolproof! I think I finally understand!

After reading your comment, I spun some elbows on a sloping pipe and it seems.....

To make a sloping pipe....

1. Level (horizontal), you need one elbow.
2. Plumb (vertical), you need two elbows....unless the slope is off by a standard elbow angle... 22.5, 45 degrees...then you only need one elbow.

Of course, for small angles, you can cock your fitting while gluing, or bend the pipe (eeek ) with a come-a-along winch, but rolling an elbow near the p-trap seems much better.

I hope I got this right because my brain is hurting.



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