The answer to 'drain trap rusty water' is that a rusty drain trap is usually caused by corrosion over time, which can lead to discolored, smelly water draining from the trap. This is a common plumbing issue that often requires repair or replacement of the trap.
Rusty drain traps are typically made of galvanized steel, which can corrode and degrade over the years, especially in areas with hard water or acidic soil. The rust buildup can restrict water flow, create unpleasant odors, and even lead to leaks. In some cases, the entire trap may need to be replaced to resolve the issue.