Connecting PVC Pipe to Steel Valve?

 I am re-plumbing part of my pool filter system. Previously,
a 3/4-inch metal valve was threaded to 3/4-inch PVC piping.
The PVC piping had a PVC male adapter, which fit into the
female threads of the metal valve. I am replacing the male
adapter but find it is a very tight fit. A lot of torque
would be necessary to get it into the previous depth.

I have a 1.25 inch metal valve connecting to a 1.25-inch PVC
male adapter with the same situation.

Do I just use teflon tape on the threads and then apply a
lot of torque until each PVC male adapter inserts at least
halfway into its metal valve?

 Elle wrote:

I find that PVC pipe, mostly from China now, varies in dia slightly,
so just screw it in until you feel it's tight. Water test for leaks &
tighten more as needed. Over tighten stresses the plastic!!

Tom J

 wrote:


  Exactly.

   Instead of 1/2 way, just make sure you have a few threads in and
you should be fine.  Use any compound you wish or no compound.

  Spend a little time at your supplier screwing in valves to the PVC
joints and find a pair that fits.

 Thank you very much for sharing your experience Tom j and
Duff. It's raining here today, so I am not doing more than a
little measuring, cutting, and gluing. I will try the teflon
piping dope.

Unfortunately the valves have to stay in place, and it's a
bad idea to replace them due to the piping starting
underground within about six inches of the valves yada. So I
can't try adapters and valves at the supply store to get a
good fit in advance.

I will report back after the job. It's a little tricky
because I have to glue other joints before I can apply the
operating pressure to the two adapter-valve joints under
discussion. And as you all know, once glued... I may put in
unions to help ease the pain of a mess-up at the valve(s),
due to yours truly not being experienced enough in plumbing.

 Hi,  just an update for the archives. I was not having any
luck with good thread contact area with the old brass gate
valves. This was even after "chasing" the threads with a
steel fitting (no tap handy). Consequently I replaced the
brass valves with new PVC ball valves, threaded. I noted in
advance how much farther the new PVC threaded fittings
advanced into the new PVC valves, Duff. Huge difference. I
used teflon tape. The joints are much more mated, due to the
male adapters' threads inserting farther. All is holding
well, plus the system is quieter when the pump is running. I
have some apprehensions about the PVC valves longevity, but
good enough for now, plus they are way less expensive than
new brass valves. Thanks again for sharing your experiences.
Elle