Tub is filled by water coming out of the jets of the tub, it’s a first for me. take a look at the cold water supply valve, does it look like it has a back flow preventer or air gap device installed?
Got a make/model #.
Where did the PVC lead to?
Better be sure before you call it out. Plumbers are expensive.
Go here Jeff.
I think it may be connected.
Working on my own report or I would get more info.solenoid on cold water line.