In article ,
Richard J Kinch wrote:

My swimming pool pump quit, and the new one is just slightly longer, so to
connect it in the space available, I need what in steel pipe you would call
a threaded nipple, except in 2-inch PVC pipe. That is, instead of gluing a
PVC male adapter, which would add too much length.

It's PVC plumbing. Rather than think about it like it's steel pipe and
make it complicated, think about it like it's PVC pipe, and it gets
simple, messy, but simple.

If it's too long, you cut it off, chop out the amount needed to shorten
it, and glue in a coupling. If you need to "stretch" it (which seems to
be your original need before the too-long fitting), you chop it off, cut
a section of pipe long enough to stretch it as much as you need, and
glue in two couplings - allowing for the center length of the coupling
in both cases. If you don't have enough room to put the coupling bodies
there, you chop it before the next fitting where there will be room for
a coupling and replace with pipe the right length and new fittings. If
you only need to add a little bit, you may need to cut some out so the
added in piece will be long enough for two couplings, or you buy a new
end fitting and only use one coupling.

Sch 40 is not normally threaded - your pool installers may have done so,
since pool plumbing is often operated at low pressure and threading
costs less than adapters, especially when you are plumbing up lots of
pools and getting out of town before they break... The HDs and Lowes of
the world (at least the ones I've been in) generally don't have any
Sch80 on site and may not be able to get any. Even Sch80 is more prone
to fail when threaded than when glued.

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