Balanced water is the difference between a pool that stays clear for weeks and one that needs rescuing every few days. Pool chemistry looks complicated, but it comes down to six numbers. This guide gives you the ideal levels, in a chart, and the order to correct them in.
Ideal Pool Water Chemistry Levels
| Measurement | Ideal range | What it does |
|---|---|---|
| Free chlorine | 1 to 3 ppm (higher for salt pools or heavy use) | Sanitizes, kills algae and bacteria |
| pH | 7.2 to 7.6 | Chlorine effectiveness, comfort, surface protection |
| Total alkalinity | 80 to 120 ppm | Buffers pH so it does not swing |
| Calcium hardness | 200 to 400 ppm (plaster 250 to 450) | Protects plaster and equipment from etching or scale |
| Cyanuric acid (stabilizer) | 30 to 50 ppm (salt pools 60 to 80) | Shields chlorine from sunlight |
| Salt (salt pools only) | 2,700 to 3,400 ppm, per your cell | Fuel for the salt chlorine generator |
Ranges differ slightly by surface and manufacturer, so treat these as the working targets for most residential pools.
What Each One Does
Free chlorine
Free chlorine is the sanitizer actually working in your water, as opposed to combined chlorine, which has already been used up. The higher the cyanuric acid, the more free chlorine you need to hold. As a rule of thumb, aim for roughly 7.5 percent of your CYA reading as a minimum.
pH
pH measures how acidic or basic the water is. Too low and the water is corrosive and irritates eyes. Too high and chlorine weakens and scale forms. Rain, heavy use, and some chlorine types push it around, so test regularly.
Total alkalinity
Alkalinity is the buffer that keeps pH from swinging. Fix alkalinity first, since it makes the other adjustments hold.
Calcium hardness
Too soft and water pulls calcium from plaster and grout; too hard and scale builds on tile, heaters, and salt cells. Fill water in some Connecticut towns is soft, in others hard, so test at opening.
Cyanuric acid
CYA is sunscreen for chlorine. Without it, sunlight destroys most of the chlorine in a couple of hours. Too much (above about 80 to 100 ppm) leaves chlorine sluggish and is only fixed by partial draining.
The Order to Balance
- Total alkalinity
- pH
- Calcium hardness
- Cyanuric acid
- Sanitizer (chlorine or salt)
Adjust one thing at a time, circulate for several hours, and retest. Our guides cover the common fixes: lowering pH and raising alkalinity, how chlorine, pH and CYA interact, and how often to shock a pool.
How Often to Test
- Weekly in season: chlorine, pH, and alkalinity at minimum.
- After heavy rain, parties, or heat waves.
- Monthly: calcium hardness and CYA.
- At opening and closing: a full panel, ideally with metals.
A test strip is fine for daily checks; a drop-based kit or a professional lab test is better for decisions. Our weekly pool maintenance includes the testing and the adjustments.
Testing Methods Compared
| Method | Good for | Limits |
|---|---|---|
| Test strips | Quick daily checks | Less precise; can misread at extremes |
| Drop-based kit (FAS-DPD, etc.) | Accurate chlorine, pH, alkalinity, CYA | Takes a few minutes; reagents expire |
| Electronic reader | Consistent readings | Cost; still needs calibration |
| Lab or pool store test | Metals, phosphates, TDS, salt | Sample must be fresh; advice can include a sales pitch |
Reading Your Results: Symptom to Cause
| What you see | Likely cause |
|---|---|
| Cloudy water, strong smell | Low free chlorine, high combined chlorine |
| Green water | Algae; low chlorine or high CYA |
| Scale on tile or heater | High pH or high calcium hardness |
| Etched plaster, irritated eyes | Low pH or low alkalinity |
| Chlorine disappears in hours | Low CYA |
| Chlorine will not hold despite adding | High CYA, organics, or algae demand |
Seasonal Tendencies in Connecticut
Spring: cold water and heavy debris; test often as the water warms. Summer: heat and swimmers consume chlorine fast and pH tends to rise. Fall: leaves and falling temperatures slow algae but increase organic load. Rain in any season dilutes sanitizer and shifts pH, so retest after storms.
Frequently Asked Questions
Which number should I fix first?
Total alkalinity, then pH. Alkalinity stabilizes pH, making the rest of the adjustments hold.
How long should I wait between additions?
Run the pump at least 4 to 6 hours after a chemical addition before retesting, and wait longer for CYA and calcium.
Do I need a different target for a saltwater pool?
Slightly. See saltwater pool maintenance for the salt pool targets.
Related Pool Care Guides
Need a Hand? Talk to Perfect Pools CT
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