The answer to 'sink rusty water' is that rusty water from a sink is typically caused by corrosion in the plumbing system. This can be due to old, galvanized steel or iron pipes that have started to rust over time. Symptoms include reddish-brown water coming from the faucet, stains on sinks and tubs, and a metallic taste or smell in the water.
The best solution is to have a plumber inspect the plumbing and determine the source of the rust. They may need to replace corroded pipes, install a water filter, or treat the water to remove rust and minerals. In some cases, the rust may be coming from the municipal water supply, in which case the homeowner may need to contact the water utility company.