Noticed pressure coming into house from water main is 120 PSI, highly recommended that a pressure reducing valve (PRV) is installed to bring pressure to 70 PSI. Hot water on faucet decreases when shower and faucet are ran at the same time. This may be happening because of the way the water piping is sized, or because the shower cartridge was affected by the high pressure. Adjusted toilet tank fill valve pressure to increase pressure of flush. Gave customer options to solve problem