Question:
What is installed in a plumbing system that prevents a surge of cold water in the shower when a toilet is flushed, or water used elsewhere in the house? Is this something that can be retrofitted in a 15 year old house?
Answer:
I would install a Moen Posi-temp shower valve which will regulate the water temperature to within plus or minus 3 degrees. I change shower valves out all the time, so I’m sure your local plumber can handle the change out for you.