I installed a new faucet set in the shower, and when I turn on the water, without pulling the diverter up, water comes out of the shower head. The flow increases, when the knob is adjusted to the highest flow of the water out of the tub nozzle.

I used 1/2" CPVC from the valve body to the tub nozzle, and I am thinking there maybe too much back pressure there. I used CPVC because I do run hot water into the tub.

Will CPVC not allow enough water flow?

Will standard PVC work, without problems from the hot water, to the tub nozzle? The diverter appears to be working open and shut, as it should.

  • yes probably too much back-pressure. possibly cause by too many sharp bends.
    – Jasen
    Commented Apr 4, 2020 at 8:19
  • Cpvc has higher temp ratings than pvc and should not cause any problems. A little piece of Teflon tape or piece of excess glue could be affecting the valve.
    – Ed Beal
    Commented Apr 4, 2020 at 9:31

1 Answer 1


I have seen this many times where a flap of PFTE tape is covering some of the pipe creating the problem even a chunk in the diverter itself , most of the spigot and shower nipples I have installed have only been 1/2” pipe so I doubt it is the size of the pipe but an obstruction causing the issue. I might pull the spigot and slip a pice of 1/2” in and turn on and see if you still have the problem , then make sure nothing got stuck in the diverter and no excess tape is covering the ends of the threaded pieces (it could always be a bad diverter if not plugged) that’s why I would test with a clean pipe.

  • Definitely pull off the spigot and test. I've had diverters loosen from the pullup knob and needed to be tightened up. Stay safe out there.
    – JACK
    Commented Apr 4, 2020 at 12:25

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