Water pressure weirdness

[Chainfire]

2. You are probably going to need a plumber

Tub faucets are generally the hardest problem for even a handy homeowner to deal with.

If it is a calcification problem, you may well need an expensive re-pipe. It is possible that you may be able to prolong necessary repairs by having the faucet serviced. In my plumbing career, I have removed pipes that were so stopped up that you could not see light through a piece 3" long; there is no easy fix for that. The buildup is like concrete and it is generally not cost effective to try to remove the buildup and save the pipe.

Call the plumber, complain about the low pressure in the faucet, it could be that a piece of trash has become lodged in a place that can can be cleared, but in the meantime, start saving some money for the long-term fix.

If you end up needing a re-pipe, try to get three estimates from three reputable plumbers.

Good luck.