hard water grout stains 2

https://remote-wiki.win/index.php/Expert_Tile_Cleaning_Phoenix:_Restoring_Your_Floors_to_Like-New_Condition

Hard water grout stains are those stubborn, chalky white or yellow-brown deposits that build up in the lines between tiles, especially in showers and sinks. They happen when mineral-rich water evaporates, leaving calcium and lime behind. Scrubbing often just spreads them, and bleach barely makes a dent, so you end up needing a specialized acid-based cleaner or a lot of elbow grease to get the grout looking clean again.