Pool Chemistry Reference Guide
Use this guide to see ideal ranges, what happens when levels drift, and which calculators to use for exact doses.
Quick reference
| Parameter | Ideal range | Too low | Too high |
|---|---|---|---|
| Chlorine | 1–3 ppm | Algae, bacteria | Irritation, odor |
| pH | 7.2–7.6 | Corrosion, discomfort | Weak sanitizer, scale |
| Total alkalinity | 80–120 ppm | pH swings | Hard to lower pH |
| Calcium hardness | 200–400 ppm | Etching, pitting | Scale, cloudy water |
| Cyanuric acid (CYA) | 30–50 ppm | Chlorine burns off fast | Chlorine lock risk |
| Shock (raise) | 10–30 ppm (temporary) | Persistent organics | Extended no-swim wait |
| Water temperature | 78–82 °F typical swim | Slow sanitizer action | Faster chlorine use |
Chlorine
Ideal: 1–3 ppm free chlorine for most swimming pools (3–5 ppm for hot tubs).
Too low: Bacteria and algae growth; cloudy or green water; combined chlorine may rise.
Too high: Eye and skin irritation; strong odor; longer wait before swimming.
Related:
pH
Ideal: 7.2–7.6 for most pools.
Too low: Metal corrosion, liner damage, swimmer discomfort, aggressive water.
Too high: Reduced chlorine effectiveness, scale formation, cloudy water, slippery feel.
Related:
Total Alkalinity
Ideal: 80–120 ppm (follow surface and sanitizer system guidance).
Too low: pH bounces when you add acid or base; unstable water balance.
Too high: pH tends to stay high; more acid needed to bring pH down.
Related:
Calcium Hardness
Ideal: Often 200–400 ppm for plaster and gunite; vinyl may run lower per manufacturer.
Too low: Water can leach calcium from plaster and grout (etching).
Too high: Scale on tile and equipment; cloudy water when paired with high pH.
Related:
Cyanuric Acid
Ideal: 30–50 ppm for outdoor chlorinated pools using stabilized products.
Too low: Chlorine lost quickly in sunlight; more frequent dosing.
Too high: Sanitizer may test high but work poorly (“chlorine lock”); harder to clear algae.
Related:
Shock Treatment
Ideal: Routine swim range stays 1–3 ppm; shock raises to roughly 10–30 ppm temporarily per label and situation.
Too low (when shocking needed): Chloramines, algae, persistent cloudiness, heavy bather load not cleared.
Too high: Bleached liners, extended no-swim times, irritation; risk if pH is also out of range.
Related:
Water Temperature
Ideal: Many pools are comfortable at 78–82 °F; chemistry targets do not change, but consumption rates do.
Too low: Slower sanitizer activity; some algaecides less effective; shorter swim season comfort issues.
Too high: Faster chlorine demand; more frequent testing in hot tubs and heated pools.
Related:
Common mistakes
- Adding chlorine before correcting pH — High pH weakens sanitizer; you may waste product. Test pH and alkalinity, adjust in small steps, then dose chlorine.
- Ignoring alkalinity — Chasing pH alone while alkalinity is far off leads to yo-yo readings and repeat chemical spend.
- Over-shocking — Doubling shock without testing volume and current chlorine can delay swimming and stress equipment. Use a shock calculator and retest.
- Shocking without running the pump — Circulation is required to distribute oxidizer and filter debris.
- Letting CYA climb unchecked — Frequent stabilized tablets without partial drains can lock sanitizer performance over a season.
- Testing only chlorine — pH, alkalinity, and CYA explain most “I added chlorine but nothing improved” cases.
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- Closing Pool Chemistry Winter
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Last updated: April 2026