The answer to 'drain rusty water' is that rusty water in your drains is typically caused by corroded plumbing pipes. This can happen over time as the metal pipes rust and deteriorate, releasing reddish-brown iron oxide particles into the water. Symptoms include discolored water, stained sinks and tubs, and a metallic taste or odor.
In many cases, the solution is to replace the affected pipes, either partially or fully, depending on the extent of the damage. This is often best left to a professional plumber, as they have the tools and expertise to properly diagnose the issue and make the necessary repairs. However, if the problem is limited to a single fixture, you may be able to address it yourself by cleaning the drain or replacing a rusted trap or pipe segment.