I have been having a water temperature problem. It affects the entire branch circuit supplying a 1st floor powder room and upstairs bath. The bath has a Kohl_r single handle mixing valve with a separate selector for side spray/shower/both. Both sinks cold supply [up and downstairs] run hot for a few minutes. The upstairs toilet fills with warm/hot water. The cold water supply pipe in basement is hot a few feet outside the wall. Happens all day/any time of day. Seems to be getting worse. After hot water is "flushed" out, water runs cold, but after only a few minutes it will be hot again?? It has some sort of scald prevention in the single handle fixtures, downstairs sink and upstairs shower. Upstairs sink is two handle version. All Kohl_r brand. No new work has been done on this branch. The fixtures were all put in the same time and worked fine for about ten years...maybe something in the "mixing valve"?