So if the pressure is to high at the faucet creating back pressure and I turn down the water at the main water shut off would that reduce the the pressure enough to stop the water from coming out the shower? I thought so but I was wrong and water still came out the shower head when filling the tub. So here's the question if reducing the pressure there doesn't help then how much help would replacing the pex line for copper be? Unless turning the water down at the main shut off only reduces the flow and not the pressure. Can anyone she'd some light on my situation. I might add that there is a considerable amount of water comin from the shower head and the shower head mixer and faucet are moen products

  • Do the instructions for the mixing valve say what type of piping to use? Do you have the simple kind of diverter which creates a blockage in the tub spout (usually pull up on a rod to pull blockage into place? – Jim Stewart Mar 22 '18 at 23:03
  • what kind of shower / tub faucet assembly do you have ? Single handle with pull ? Can you take picture or post model of faucet .. What it sounds like to me is the unit was somehow connected wrong ..(shower and faucet lines as incoming supply and the incoming supply lines to the shower / tub )??? – Ken Mar 23 '18 at 7:06
  • I will take some pic's a little later today and double check if its connected wrong as you say but for now it's moen with the single pull handle and yes I believe it's the simple diverted as well – Derek McCluskey Mar 23 '18 at 12:48
  • There are on-off valves that one can install just before the shower head. This would stop water coming out the shower when you want water for the tub. The purpose of these valves is for water conservation during showering, but it would work to solve your problem. signaturehardware.com/… – Jim Stewart Mar 23 '18 at 14:40

Sounds like you used PEX to run from the mixer valve to the tub spout. Replace the PEX that goes from the mixer to the spout with copper. You are getting a bypass to the shower because the PEX from the mixer to the spout cannot handle the flow without backing up to the shower head. PEX has a slightly smaller i.d. than copper.

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