Pool Water Chemistry Basics: The Numbers That Matter

By Imperial Valley Pool Services · Updated 2026-10-23

Healthy pool water comes down to a handful of readings: free chlorine 1–3 ppm, pH 7.2–7.6, alkalinity 80–120 ppm, stabilizer (CYA) 30–80 ppm, and calcium hardness 200–400 ppm. Saltwater pools also need salt in the range their cell calls for, usually 3,000–3,600 ppm.

Clear water is not the same as balanced water. A pool can look fine and still be eating your equipment or growing algae you can't see yet. These are the readings we check on every visit and the ranges we aim for.

Free chlorine: 1–3 ppm

Free chlorine is the sanitizer doing the work. Too low and algae and bacteria get a foothold. Too high is uncomfortable for swimmers and hard on a pool surface and liners. In our heat, chlorine burns off fast, which is why stabilizer matters.

pH: 7.2–7.6

pH controls how well chlorine works and how the water feels. Below about 7.0 the water turns acidic and can etch plaster and corrode metal parts. Above about 7.8 chlorine gets sluggish, scale forms, and water can turn cloudy.

Total alkalinity: 80–120 ppm

Alkalinity is the buffer that keeps pH from swinging. If alkalinity is low, pH bounces around. If it is high, pH keeps drifting up and is stubborn to bring down. Fix alkalinity first, then pH.

Cyanuric acid (CYA): 30–80 ppm

CYA is sunscreen for chlorine. Without any, direct sun can destroy much of your chlorine within hours. Too much, and the chlorine you do have becomes less effective.

Calcium hardness: 200–400 ppm

Our tap water comes from the Colorado River and is already hard. As pool water evaporates, minerals stay behind and calcium creeps up. Very high calcium leaves white scale on tile and inside heaters and salt cells.

Salt: about 3,000–3,600 ppm (saltwater pools)

Salt systems make their own chlorine. Each cell has a recommended salt range, so check your equipment manual and use it over any general number.

The order to fix things

Test the water before adding anything.
Correct total alkalinity.
Adjust pH.
Set stabilizer and calcium if they are far off.
Bring chlorine to range last, then retest after the water circulates.

Don't want to manage any of this? Our weekly pool service tests every reading on every visit and sends you the results with photos.

Frequently asked questions

How often should I test my pool water?

At least once a week, and again after heavy use, a dust storm, or a rain. In summer heat many owners test two or three times a week. Our technicians test every reading on every visit.

Can I use test strips?

Strips are fine for a quick check between visits, but they are less precise than a liquid drop kit or a photometer, especially for chlorine and alkalinity. If a strip result looks surprising, confirm it with a better test.

What is the most common reading people get wrong?

Stabilizer (CYA). It is easy to overlook, and once it climbs too high the only fix is to replace part of the water.