Pool water chemistry sounds intimidating — but once you understand the basics, maintaining a balanced pool becomes second nature. This guide breaks down every key parameter in plain English, explains why it matters, and tells you exactly what to do when something is off.
The Big Five Parameters
1. Free Chlorine (FC) — The Sanitizer
Chlorine is your pool's primary defense against bacteria, algae, and viruses. Free chlorine is the active, available chlorine in your water. Keep it between 1–3 ppm for a standard chlorine pool.
2. pH — The Balance Point
pH measures how acidic or basic your water is. The ideal range is 7.4–7.6. Low pH (acidic) corrodes equipment and irritates eyes. High pH (basic) reduces chlorine effectiveness and causes cloudy water. pH is the most important parameter to keep in range — it affects everything else.
3. Total Alkalinity (TA) — The pH Buffer
Alkalinity acts as a buffer that prevents pH from swinging wildly. Keep it between 80–120 ppm. Low alkalinity causes pH to bounce around unpredictably. High alkalinity makes pH hard to adjust and can cause cloudy water.
4. Cyanuric Acid (CYA) — The Chlorine Protector
CYA (also called stabilizer or conditioner) protects chlorine from being destroyed by UV rays. Without it, sunlight can wipe out your chlorine in a matter of hours. Keep CYA between 30–50 ppm for a chlorine pool, or 60–80 ppm for a salt water pool. Too much CYA (over 100 ppm) makes chlorine ineffective — the only fix is a partial drain and refill.
5. Calcium Hardness (CH) — The Plaster Protector
Calcium hardness measures the amount of dissolved calcium in your water. Keep it between 200–400 ppm. Low calcium causes water to leach calcium from plaster, grout, and equipment. High calcium causes scaling and cloudy water.
The Order of Adjustments
Always adjust in this order: Alkalinity → pH → Chlorine → CYA → Calcium. Adjusting alkalinity first stabilizes pH, making it easier to dial in.
Testing Frequency
Test your water 2–3 times per week during swim season, and after heavy rain or heavy bather load. A quality 7-in-1 test kit gives you all five readings in under two minutes.