The answer to 'supply line rusty water' is that rusty water coming from a supply line is typically caused by corrosion or rust buildup inside the pipe. This can happen over time as the metal in the pipe degrades, especially in older homes or areas with hard water. Symptoms include reddish-brown discoloration in the water, a metallic taste, and potentially low water pressure.
In some cases, this can be a DIY fix, such as flushing the line or replacing a section of the pipe. However, if the issue is widespread or the supply line is difficult to access, it's best to call a professional plumber. They can properly diagnose the problem, clear the line, and replace any damaged components to restore clean, reliable water flow.