According to the Uniform Plumbing Code (the code that the California Plumbing Code is based on) water pressure must be below 80 psi. If city pressures are above this limit, a pressure reducing valve must be installed to lower the pressure to a legal amount. An ideal pressure is in the 60 psi range. This is to protect your fixtures and pipes but will also save an enormous amount of water that is currently being wasted at higher pressures.
This water heater was replaced just a few days ago. It’s failure was brought on, in part, by the high water pressures in the area. By reducing the incoming pressure, you can prolong the life of fixtures like water heaters, faucets, electronic solenoids in dishwashers and washing machines and water treatment equipment. For a small investment of a few hundred dollars, you can protect thousands of dollars worth of plumbing fixtures and piping, not to mention the possible and costly cleanup should something fail inside the home. Take care of your plumbing and it will take care of you.