After leveling shower floor for new shower base, I need to raise height of 2" drain pipe about 1.75" to accommodate a "no-caulk" base drain. The pipe is buried in concrete foundation.

I found a pipe extender marketed for pool plumbing with a 1.25" L narrow end that fits inside the 2" pipe, and gives me an extra 1.25" of height.

This reduces a portion of the internal diameter of the pipe to roughly 1.75". Will that quarter inch loss be significant enough to slow drainage in a meaningful way? Once it's in and shower redone, there's no going back!

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  • how do you plan to connect them to make it leak tight
    – Traveler
    Jul 2, 2022 at 16:52
  • @knowitall - PVC cement, but I've never worked with PVC before, so open to better ideas.
    – Scott
    Jul 2, 2022 at 16:59
  • what about going the other way, slip a 2" extender over the 2" pipe, how much pipe is sticking out of the concrete ?
    – Traveler
    Jul 2, 2022 at 17:08
  • @knowitall - only 1" above concrete. Not sure it would work. Drain tops made for acrylic shower bases that I've found are made to go on the outside of 2" pipes.
    – Scott
    Jul 2, 2022 at 17:41
  • So it might work with 2 in. PVC Schedule 40 S x S Coupling, without using glue, glue scares me, it is so permanent. Since it is not a pressure pipe you might get away with just a o-ring
    – Traveler
    Jul 2, 2022 at 18:19

1 Answer 1


Is 1.75" .vs. 2" significant? (if schedule 40, as is likely/common, actually 2.067" ID for the drain pipe)

Math makes all clear. If you want to do the whole thing, the area of the pipes are Pi * r**2 (Pi r-squared) though the relationship (which is all we really need to know) is the same if you just look at d**2

1.75 squared is 3.0625

2 squared is 4

2.067 squared is 4.272489

So your reducer is 71.68% of 2" schedule 40 pipe. Or reduces the area by 28.32% if you prefer that view.

More simply, most plumbing codes require a 2" shower drain, so if you need to chisel a bit into the concrete to do the extension correctly to code, get chiseling, because it's going to be a major bother to have to remove the shower if your inspector fails it after you've installed a non-approved part. Chiseling concrete looks easy by comparison.

  • trying to avoid undoing and redoing the concrete/leveling. Found a video by a plumber demonstrating how to remove glued pipe from fitting, by making multiple cuts in the pipe, then gently prying out each part. Thoughts? youtu.be/-CpgYUpNXaQ?t=799
    – Scott
    Jul 2, 2022 at 21:31
  • Heatgun and pliers works easier, IME. But you might want to practice a bit before going at your actual cemented in place fitting.
    – Ecnerwal
    Jul 3, 2022 at 0:08

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