I recently changed out the tub faucet in my master bath, and switched it from copper pipe to pex at the same time. Since then I have such dismally low water pressure, it takes 25 minutes to fill the tub. What is the most likely source of the problem?
Not the pex. Would be something with the valve. Modern valves are designed to be low flow to conserve water, they usually have a limit setting so you do not scald yourself with hot water.
Simply more complicated then the older valves. I would suggest pulling out the directions and reading through it to see the options and settings you have.
Trash got knocked loose and is plugging up the posts in the control valve.
Anti scald valve has trash in it.
1/2" Pex was used instead of 3/4" (I've used 1/2" many times for the supply and never had an issue, but we have no way of knowing how long your runs are)