need help for parents: hot/cold water balance problem
I am visiting my elderly parents, and need some quick advice. They have an old (60 yrs.) shower stall, i.e., there is no tub. Hot and cold water both come to shower head; however, as soon as essentially any cold is turned on, the hot goes to about zero. This confuses me a bit because there is no tub/shower valve to worry about. Were thermostatic mixing valves (or something like them) in use 60 yrs ago?
There is no (easy) access to the back of the plumbing. (Will have to remove drywall.) I don't mind doing that, but want to have an idea of what I should be doing once I am in there before ripping apart their bathroom.
My elderly parents thank you in advance for any tips!