The answer to 'why is my gutters water stains' is that water stains in your gutters are typically caused by a buildup of debris, improper gutter installation, or a problem with the gutter system. Over time, leaves, twigs, and other organic matter can accumulate in your gutters, preventing proper drainage and causing water to overflow and stain the sides of the gutters.
Another common cause is improper gutter installation, where the gutters are not angled correctly or have gaps and leaks that allow water to seep out and stain the surrounding areas. Additionally, a damaged or clogged downspout can also contribute to water stains, as the water has nowhere to properly drain.