I have a 1.5" P trap under my bathtub in a mobile home. If I have to use a coupler to join a pipe I cut, would I use a 1.5" coupler or a 2" coupler? The hardware store said 2", but I question that. Thanks

Hi Fisher...

The outside diameter of 1.5" PVC or ABS pipe is 1-7/8" with an 1.5" inside diameter, of course.

If you have an 1.5" pipe/ptrap then you want to purchase an 1.5" coupling to join/add anything to the pipe.

The confusion is probably in that the coupling measures a 2"+ diameter, but it fits an 1.5" pipe, OK?

Mark

So... I want to purchase a 1.5" but the 2" fits the 1.5" pipe? O_o
I already bought the 2x2" coupling, is that wrong or right? Lol sorry I'm inexperienced.

You need to take a tape measure and measure across the pipe to be sure. See diagram below for a visual... ;)

As above, The outside diameter of 1.5" PVC or ABS pipe is 1-7/8" with an 1.5" inside diameter, of course.

The 2"x2" coupling should measure about 2-3/8" inside diameter... too large for 1.5" pipe.

Mark