# Safe to use this narrowing 2" PVC extension in shower drain?

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!

• how do you plan to connect them to make it leak tight Commented Jul 2, 2022 at 16:52
• @knowitall - PVC cement, but I've never worked with PVC before, so open to better ideas. Commented 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 ? Commented 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. Commented 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 Commented Jul 2, 2022 at 18:19

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 Commented 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. Commented Jul 3, 2022 at 0:08