Shower pressure variations

[mbailey5]

I want to rebuild my 2nd floor master shower with a digital shower control system and multiple heads/jets. The current feed is a single 1/2" copper line. I used a pressure gauge with garden hose thread and a 1/2" NPT adapter to measure the pressure at the shower head. The pressure with the valve turned completely on halfway between cold and hot is 32 pounds. However, if a sink faucet anywhere in the house is turned on, the shower head pressure drops to 24 pounds. If a toilet is flushed with no faucets on, the pressure at the shower head drops to 20 pounds. The existing shower suffers from temperature changes when other faucets are in use. The house was built in 1994, it is on Tucson city water, the water heater was replaced in 2013, and I have a water softener installed where the water line enters the house. There is a pressure regulator valve at the point of entry to the house but I was told that setting the pressure higher could be dangerous to my plumbing (pvc and copper) or outdoor irrigation (pvc and 1/2" poly) and that it probably would not solve the pressure variations I see at the shower. Although I plan to rebuild the shower myself, I will get a plumber to modify or install additional water lines (I like the DIY route when I know what I'm doing but, while I have experience with sweating pipes and running pvc for sprinklers, in-ground swimming pools, etc, I have little interior plumbing knowledge). How can I determine why such large pressure changes occur? I don't know whether a larger shower supply line must be run to allow the new system to be installed or if some sort of intermediate pump could solve the problem. On a related topic, any input on digital systems to look for or avoid would be appreciated. Cost is definitely a factor and I see them online from $800 to $5,000.

 

[phishfood]

If cost is a big concern, I would reconsider a multi head shower system. Big shower systems can be tricky to install correctly, even some plumbers don't know how to do them correctly.

While I would not run a multi head shower system from 1/2" copper if I had the choice, there are a few of the smaller systems out there that have 1/2" inlets that do OK. Still better to supply them with 3/4", though.

From your description, it sounds as though you have a problem with the main water supply, not so much with the water distribution inside of the house. That will need to be addressed first, or you will not be happy with the result no matter what size pipe you run, or what shower valve you install.