What August does to chlorine
Warm water speeds up every reaction in the pool. Chlorine is consumed faster by sunlight, by swimmers and by the algae spores that arrive with every breeze. A pool that held 3 ppm chlorine on a weekly dose in May can drop to zero in three days in August.
The three numbers that matter
Stabilizer (cyanuric acid) between 30 and 50 ppm shields chlorine from UV; without it, half your chlorine is gone by lunchtime. Free chlorine at 3–5 ppm in peak summer, not the 1–2 ppm printed on the test strip bottle. Phosphates under 500 ppb, because phosphates are algae food and Houston tap water and lawn fertilizer both add them.
Storms and the dilution problem
A typical Gulf Coast downpour adds inches of unchlorinated water and washes fertilizer into the pool. After a big storm, expect to test and re-dose within a day, not at the next scheduled visit.
Circulation and the filter
Run the pump at least eight to ten hours in August, more for a single-speed pump. A filter that is overdue for cleaning cannot remove the algae the chlorine kills, so the water stays cloudy and the bloom returns. Clean it every three to four months.
Questions
My pool is already green. What now?
A controlled shock, brush and filter sequence over about three days brings most pools back. Our green pool cleanup is a flat $300 including chemicals.
Should I add algaecide every week?
A maintenance algaecide helps in heavy shade, but the real fix is keeping chlorine and stabilizer in range. Algaecide does not replace chlorine.