What commonly causes stains on the interior pool surfaces?

Stains on the interior surfaces of a pool can be attributed to various metals that naturally occur in water or are introduced through different means. Copper, manganese, and iron each contribute to discoloration in distinct ways. Copper, often from pipes or algaecides, can lead to green or blue stains. Manganese is known for causing dark brown or black stains, particularly in areas with high mineral content in the water. Iron tends to leave reddish-brown stains, commonly seen when rust or iron-rich water is present. Each of these metals can interact with chlorine and other pool chemicals, resulting in visible stains. The presence of all these elements indicates that a comprehensive understanding of water chemistry is crucial for pool maintenance, confirming that all three metals can be potential culprits in staining. This is why the selection that encompasses all these options together highlights a holistic view of common causes for staining in pool interiors.