We had a deadly combination of low pH and copper piping, and after 35+ years, pinhole leaks developed. We had never had our water treated for low pH because we didn't know it was problematic. The first leak caused over $3,000 in damage. Since we had no way of knowing how extensive the leaking problem was, or where other leaks might (or already had) develop(ed), we decided to replace all of the piping.
We did consider PEX, but (and this will probably sound like a copout) the repipe project was something my husband was handling, and for reasons I can't recall at the moment, the decision was made to go with CPVC.
It will not matter, because all of the water used when flushing comes from the toilet's tank.
Most toilets do not rely on water pressure to flush, only gravity.
Have you done the flow measurements into a bucket as I suggested? It is premature to talk about pipe size if the shower valve is the limiting factor. Pipe size affects pressure only relative to flow. Right now, I suspect the shower head is the limiting factor.
Have you taken elevation into consideration? How much elevation difference is there between where the pump pressure switch is and where the shower head is? You can count on .43 PSI loss for every foot of elevation.
Thank you for the feedback.... you do have the relatively uncommon, but the one situation ( low ph) where copper has problems. Doing a repipe with the relatively unflexible CPVC must have been a chore.
FWIW, both CPVC and PEX have a lower flow capacity verses copper based on the same nominal size. This is because the outside of the pipe is what is controlled, not the inside, so because the plastic pipes need more strength, their walls are thicker, thus, the ID is smaller.
What would have worked better was to have 3/4" pipe running to the shower, then converting to 1/2" (which is probably the valve's inlet size, although some are 3/4" or even larger). Most things can function fine on 1/2", but high flow or multiple fixtures off one line need a larger supply coming into the area, then branching off with smaller pipes, where appropriate. If they ran 1/2" to the bathroom group, you'll find a real issue if someone flushes the toilet or tries to run the vanity sink while you're in the shower!
40-60 does a fine job with the right shower head. I would speculate that the majority of homes in the U.S. have less than 60 psi.
So now my question is, is this more a matter of increasing the water pressure, or changing the CPVC from 1/2" to 3/4"? Or should we do both?
I'm expecting my plumber here today and I'll certainly have a conversation with him about this.