I've never used the Brita filter on the MX water in my tanks ... even the Mexicans buy water for drinking. Just is safer to do. But I do use it for cleaning my fruits and veggies ... after it's been in the chlorine AND using drops to put in the water also.
When I leave MX, I empty my tanks, refill with chlorine and water (like we do to clean the tanks here) and empty, etc. Just precautionary. I don't like getting sick.