If it's a male cat, especially a neutered one, be sure that he is not having difficulty urinating. When male cats have a urinary blockage from the formation of crystals in their urethra, they will often go in a sink or tub to try to urinate. Best prevention is limiting dry food and promoting hydration with a water fountain.
mrcanslim t1_j1mvdoh wrote
Reply to [OC] Why is my cat obsessed with the sink? by Uptownflunk
If it's a male cat, especially a neutered one, be sure that he is not having difficulty urinating. When male cats have a urinary blockage from the formation of crystals in their urethra, they will often go in a sink or tub to try to urinate. Best prevention is limiting dry food and promoting hydration with a water fountain.