Crystal water in spring is earned in fall. When the swim load drops and water cools, chemistry behaves differently. Lock in balanced water now to prevent stains, scale, and algae during the months you’re not paying attention.
Start with Reliable Testing
Use a fresh liquid test kit or calibrated digital meter—strips are fine for quick checks but can drift. Record current readings so you can track trends during occasional winter check‑ins.
Hit the Big Four
pH (7.2–7.6): Cooler water holds CO₂ differently, so pH tends to rise more slowly. Adjust into range; too high invites scale, too low etches plaster.
Total Alkalinity (80–120 ppm): Acts as a buffer against pH swings. If you’ve battled pH bounce all summer, stabilizing TA now will make winter hands‑off.
Calcium Hardness (200–400 ppm): Arizona’s hard water complicates this—test fill water too. If CH is very high, use a scale inhibitor and keep pH at the lower end of normal.
Free Chlorine: Shock to breakpoint to oxidize organics, then maintain a conservative level appropriate to your chosen sanitizer.
Support Crew: Stabilizer, Enzymes, Algaecide
Cyanuric acid (30–50 ppm for chlorine pools) shields sanitizer from UV on bright winter days. Enzymes digest lotions and oils that create scum lines. A polyquat algaecide provides long‑lasting protection without copper staining.
The Langelier Saturation Index (LSI)
Use LSI to ensure water is neither scale‑forming nor corrosive. Target a slightly negative to neutral winter LSI (‑0.2 to 0.0) to reduce calcium fallout on tile and heaters as water cools.
Final Steps
Brush thoroughly after chemical additions, run the pump to mix, and then cover the pool. Re‑test monthly; a 5‑minute tweak beats a spring cleanout.
