Litter box location is of prime importance for your cat to use it successfully. But as your cat ages, you may have to re-look the location because problems associated with age may make your cat avoid the litter box. For example, if the box is kept in a basement, mobility issues may prevent your kitty from descending the basement stairs to get to the box, or, getting into the box at all. If you think about it in human terms, would you expect your 96-year-old grandmother to go up and down to the basement several times a day to go to the toilet? Thus consider repositioning the box on the level in the home your cat lives on the most.
If your cat loves to drink water from a running tap, consider getting a drinking fountain for her. Cats in the wild drink running water and a pet drinking fountain recreates this in the home.