Sorry for hijacking the thread. I posted a question originally but got little response. At any rate, I have fixed the problem. On close examination, The Rheem heater did indeed have the "heat trap nipples"(pictures on Rheem's website, and available at Home Depot). Yesterday I cut the CPVC inlet line (it seemed obvious it was an inlet problem), removed the valve, nipple and associated copper piping. The ball in the heat trap nipple was jammed, as suggested. The workings in the nipple appeared to be damaged, probably from the original installation. I replaced the nipple with an open dielectric nipple, no heat trap. I chose high flow over efficiency. I installed a union, anticipating that Murphy's law would dictate a leak somewhere. Luckily, no leaks. The original nipple was incredibly difficult to remove. I had to heat it with a torch, and use an extender bar on my pipe wrench(again, luckily , nothing broke). I now have wonderful flow, 40psi with 3 faucets running. Thanks for all the suggestions, and I apologize if I broke protocol by hijacking the thread.