Then a Houston rainstorm rolled through, and suddenly the water doesn't look quite as inviting. Maybe it's slightly cloudy. Maybe there's a green tint developing. Or perhaps the pool looks fine, but the chlorine reading has dropped dramatically.

July brings together several factors that challenge water quality. High temperatures encourage algae growth. Afternoon thunderstorms dilute carefully balanced chemicals. Wind carries pollen, leaves, grass clippings, and dust into the water. Add a weekend full of swimming, sunscreen, and backyard entertaining, and your pool has a lot more work to do than it did in the spring.