Pool Water Chemistry: Balancing, Testing & Shocking

Balanced water comes down to seven numbers. Keep them in range and your pool stays clear, comfortable and easy on equipment. Always adjust in this order: alkalinity → pH → calcium → sanitizer, because alkalinity anchors pH and pH controls how well chlorine works.

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The 7 numbers that keep your pool perfect

• Free chlorine: Ideal 1–3 ppm (3–5 ppm for salt pools). Kills bacteria and algae. Too low: algae and cloudy water. Too high: eye and skin irritation.

• pH: Ideal 7.4–7.6. Controls comfort and chlorine strength. Too low: etching, corrosion, stinging eyes. Too high: scale, cloudy water, weak chlorine.

• Total alkalinity: Ideal 80–120 ppm. Buffers pH so it stays steady. Too low: pH swings ("pH bounce"). Too high: pH drifts up and scale forms.

• Calcium hardness: Ideal 200–400 ppm. Protects plaster and surfaces. Too low: etched plaster and pitting. Too high: white scale on tile and equipment.

• Cyanuric acid (stabilizer): Ideal 30–50 ppm (60–80 for salt pools). Shields chlorine from the sun. Too low: chlorine burns off in hours. Too high: chlorine "locks" and loses power.

• Salt (salt pools only): Ideal 2,700–3,400 ppm. Feeds the salt cell to make chlorine. Too low: the cell stops producing. Too high: corrosion and salty taste.

• Total dissolved solids (TDS): Ideal under 1,500 ppm above your fill water. A general water-age indicator. Too high: dull, hard-to-balance water, which means it is time to drain and refresh.

Tip: Know your pool’s volume in gallons before adding anything, because every dosage depends on it. For a rectangle: length × width × average depth × 7.5.

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How to test your pool water

Test chlorine and pH 2–3 times a week in summer (once a week in winter), and run the full panel once a month.

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Testing methods

• Test strips: Best for quick daily checks. Fair accuracy, low cost.

• Liquid / drop test kit: Best for a weekly full balance. Good accuracy, low to medium cost.

• Digital tester or photometer: Best for precise readings and salt pools. Very good accuracy, medium to high cost.

• Blue Kiwi tech test: Best for a monthly check-up or problem water. Professional accuracy, included with service.

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Step by step (drop kit)

1. Take the sample from elbow-deep water, away from return jets and skimmers.

2. Fill each vial to the marked line.

3. Add reagent drops exactly as directed; don’t hold the bottle sideways.

4. Compare the color against a white background in daylight, not direct sun.

5. Write the numbers down (or log them in an app) so you can spot trends.

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How to sanitize and shock your pool

Chlorine keeps the water safe every day. Shocking is a periodic super-dose that burns off contaminants your daily chlorine can’t keep up with.

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Daily sanitizing options

• Chlorine tablets (trichlor) in a floater or feeder: Slow, steady chlorine plus stabilizer. Watch out: raises CYA and lowers pH over time.

• Liquid chlorine: Fast, with no stabilizer added. Watch out: needs adding every 1–2 days in summer.

• Salt chlorine generator: The salt cell turns salt into chlorine. Watch out: clean the cell every 3 months, because scale builds fast in hard water.

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When to shock

• Once a week in summer, every 2 weeks in cooler months

• After heavy swimmer use, a party, or a dust storm

• When the water smells strongly of “chlorine” (that smell is used-up chlorine, not too much)

• At the first sign of algae or cloudiness

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How to shock (step by step)

1. Test and adjust pH to 7.4–7.6 first.

2. Wait until dusk. The Arizona sun destroys unstabilized chlorine within hours.

3. Pre-dissolve granular shock in a bucket of pool water (never add water to chemicals).

4. Pour slowly around the edge with the pump running.

5. Run the pump overnight; swim once chlorine falls back below 5 ppm.

Safety: Never mix different chemicals together, store them dry and shaded, and keep them away from kids and pets.

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Rather let us handle it? Book a Blue Kiwi service visit.