pH (7.2-7.6)
pH measures acidity/alkalinity. Low pH (<7.2) causes eye irritation, plaster etching, and metal corrosion. High pH (>7.8) reduces chlorine effectiveness and causes scale buildup. Muriatic acid lowers pH; soda ash raises it.
Free Chlorine (1-4 ppm)
Chlorine is your primary sanitizer. Below 1 ppm, bacteria and algae can grow. Above 5 ppm, swimming becomes uncomfortable. Maintain 2-4 ppm for optimal sanitation and comfort. For salt pools, the salt cell produces chlorine automatically.
Total Alkalinity (80-120 ppm)
Alkalinity buffers pH, preventing rapid swings. Low alkalinity causes pH bounce. High alkalinity makes pH difficult to adjust. Sodium bicarbonate raises TA; muriatic acid lowers it.
Calcium Hardness (200-400 ppm)
Too-low calcium causes the water to become aggressive and dissolve plaster and metal fittings. Too-high calcium causes scale deposits on surfaces and equipment. Calcium chloride raises hardness; dilution (draining and refilling) lowers it.
Pro Tip
In hard-water areas, monitor calcium closely - scale buildup is one of the most common and expensive problems to fix.
Cyanuric Acid / Stabilizer (30-50 ppm)
Stabilizer protects chlorine from UV degradation. Without it, sunlight destroys chlorine within hours. Too-high levels (>80 ppm) reduce chlorine effectiveness, requiring partial drain. This is the most misunderstood pool chemical.