Hard water

Hard water carries a lot of dissolved calcium and magnesium. In a pool, that means faster scale on tile, heaters, and salt cells, mostly in warm weather.

You can test your tap water for hardness before you fill the pool. If it is high, plan to dilute with a partial drain and refill when calcium climbs. Keep pH and alkalinity in range so scale does not form. Test your fill water each time you top off the pool, since the minerals add up over a season.