Reading and Interpreting Your Pool Water Test Results

Why test pool water regularly

Pool water shifts constantly under sunlight, bathers, rain, and the products you add to treat it. Testing regularly helps you catch an imbalance before it turns into cloudy water, itchy eyes and skin, or premature wear on your pool's surface and equipment. The ranges below are commonly cited and meant as general guidance only: always check the label on your own products and any guidance from your pool surface or equipment manufacturer, since recommended ranges can vary by pool type.

pH: the baseline balance

pH measures how acidic or basic the water is. It's the most-watched number because it affects both how well chlorine works and how comfortable the water feels.

• Commonly cited range: roughly 7.2 to 7.6.
• Too low (acidic water): stinging eyes, corrosion of metal fittings, faster wear on liners and gaskets.
• Too high (basic water): cloudy water, scale buildup, reduced chlorine effectiveness, dry or itchy skin.

pH can swing from one day to the next, especially after heavy bather load or a storm — that's normal, but check it before adjusting chlorine.

Free chlorine and combined chlorine (or bromine, or salt)

Free chlorine is the portion still available to disinfect the water. Combined chlorine forms when chlorine reacts with organic material — sweat, lotions, urine — and is far less effective at disinfecting; it's also the main source of the sharp "chlorine smell" often mistakenly blamed on too much chlorine.

• Free chlorine: a commonly cited range is roughly 1 to 3 ppm.
• Combined chlorine: ideally close to zero; a rising value suggests the water needs a shock treatment or a partial water change.
• Too low: higher risk of algae and bacterial growth, water going cloudy.
• Too high: irritated eyes and airways, fading on some equipment or surfaces.

Bromine pools follow a different scale, and saltwater pools generate their own chlorine through a salt cell — in both cases, follow the range your system's manufacturer specifies rather than standard chlorine benchmarks.

Total alkalinity: fix this before pH

Total alkalinity measures the water's ability to keep pH steady rather than swinging wildly. It's a less intuitive number, but it drives everything else: unstable alkalinity makes pH "bounce back" shortly after you correct it.

• Commonly cited range: roughly 80 to 120 ppm.
• Too low: pH becomes unstable and swings sharply day to day.
• Too high: pH becomes hard to bring down and tends to drift upward again.

That's why the usual correction order is: adjust total alkalinity first, then fine-tune pH afterward. Correcting pH before alkalinity often means having to redo it again shortly after.

Calcium hardness, stabilizer, and temperature

Three more parameters round out the picture, with a slower but real impact over time.

• Calcium hardness: water that's too soft tends to become aggressive toward surfaces and grout; water that's too hard encourages chalky scale deposits. A commonly cited range is roughly 150 to 250 ppm, adjusted for your pool's surface type.
• Cyanuric acid (stabilizer): it shields chlorine from UV breakdown in sunlight, but too much can actually reduce how effectively free chlorine works (sometimes called chlorine "lock"). Guidance commonly points to staying under roughly 50 ppm, with levels usually creeping up from repeated use of stabilized chlorine tablets.
• Temperature: warmer water speeds up chlorine consumption and favors algae growth, which raises treatment needs in summer. Typical comfortable swimming ranges are cited around 78–82°F (about 26–28°C).

Salinity and TDS (total dissolved solids)

TDS covers all the salts and minerals dissolved in the water, including those added gradually through treatment products. A steadily climbing TDS reading can be a sign that it's time for a partial water change, since heavily mineralized water becomes harder to balance and can look dull. In saltwater pools, salt level is measured separately and should stay within the range set by the salt cell manufacturer.

Which order to correct things in

When several readings are off at once, a set order avoids chasing your tail: total alkalinity first, then pH, then chlorine, and finally slower-moving parameters like calcium hardness or stabilizer. This order follows from how the parameters interact — alkalinity governs how stable pH is, and pH in turn governs how effective the measured chlorine actually is.

Some of these readings (pH, temperature, calcium hardness, alkalinity and dissolved solids) combine into the Langelier Saturation Index (LSI), which shows whether water tends toward scaling or corrosion. Chlorine is not part of it: a near-zero LSI says nothing about sanitation, which you check separately. Our guide to the Langelier Saturation Index explains how it's calculated and read.

What Cavrya does with this

In the Cavrya app, you enter your own test readings. The app then shows your water balance (Langelier Saturation Index), the associated corrosion or scaling risk, a suggested corrective dosage, and a history of your past tests so you can track how your pool changes over time.