The answer to 'why is my drain rusty water' is that rusty water in your drains is typically caused by corroded metal pipes. Over time, the iron in the pipes can start to break down, leading to rust and discolored water. This is a common issue, especially in older homes with galvanized steel or cast iron plumbing.
Some common symptoms of rusty drain water include reddish-brown or orange-colored water, a metallic taste, and potential staining of sinks and tubs. The rust can also build up and clog the drain, leading to slow or backed-up drainage.