The answer to 'why is my sink rusty water' is that the rusty water is likely caused by corroded or old plumbing pipes. Over time, metal pipes can start to rust and deteriorate, causing discolored, rusty-looking water to come out of your sink faucet.
Some common symptoms of rusty sink water include reddish-brown stains in your sink, a metallic taste or odor to the water, and visible flecks or particles in the water. This is a sign that the pipes supplying water to your sink need to be addressed.