Pool Chemistry Chart: Target Ranges and What Each Reading Means

Chart 1: public-health and industry ranges

Pentair’s manual introduces its table as what “the Pool and Hot Tub Association (PHTA) recommends,” and adds “DO NOT USE CYANURIC ACID IN INDOOR POOLS.” The MAHC is written for public pools and isn’t binding on a backyard pool, but it is the most detailed public-health standard.

Chart 2: salt chlorine generator makers

Hayward says its table summarizes “levels that are recommended by The Association of Pool and Spa Professionals (APSP),” and that “the only special requirements for the AquaRite are the salt level and stabilizer.” If you run a salt system, its manual comes first. The salt chart guide covers how much salt to add, and the salt chlorine generator list compares current models from these three makers.

What each reading means

Free chlorine

Free chlorine is the chlorine available to kill germs. CDC says “chlorine and pH are the first defense against germs that can make swimmers sick,” and that many things lower chlorine, including “pee, poop, sweat, and dirt from swimmers’ bodies, as well as sunlight.” CDC also warns that above 10 ppm, a DPD test “might partially or totally bleach out, resulting in a false low or 0 ppm chlorine result.”

Low readings call for more chlorine from a labeled product. See the pool shock comparison and the 3-inch chlorine tablet list .

Combined chlorine

The MAHC defines combined chlorine as chlorine “present in the form of inorganic or organic chloramines,” which is “less reactive than free available chlorine.” It is calculated as total chlorine minus free chlorine. The MAHC annex says chloramines form when chlorine combines with compounds “such as urea, amino acids, and ammonia from perspiration and urine.” Above 0.4 ppm, the MAHC requires public pools to act, for example by superchlorination or water exchange.

pH

CDC says the 7.0–7.8 range “best balances killing germs to prevent swimming-related illness, the lifespan of the pipes, and swimmers’ comfort.” Chlorine works less well as pH rises, “especially if pH is >8.0,” and pipes are more likely to corrode below 7.0. The pH and alkalinity guide covers adjusting it.

Total alkalinity

The MAHC annex calls total alkalinity the water’s buffer, which “helps prevent wide variations in pH (pH bounce).” Too low and pH swings quickly; too high and “pH becomes difficult to adjust.” If you use stabilizer, Pentair and the MAHC annex both say to subtract one-third of the CYA reading from the alkalinity result.

Calcium hardness

The MAHC annex says 200–400 ppm “is preferred for proper calcium carbonate saturation,” or 100–200 ppm for water above 90°F. “Too much calcium causes cloudiness and scale formation,” while too little, especially with low pH or alkalinity, can make water “aggressive,” dissolving plaster and metal parts.

Stabilizer (CYA)

CircuPool’s manual says sunlight “can destroy unstabilized chlorine in as quickly as 2 hours,” and stabilizer slows that loss. The catch, CDC notes, is that “disinfection times are longer in the presence of cyanuric acid,” and CDC’s minimum free chlorine doubles from 1 to 2 ppm when CYA is used. Trichlor tablets and dichlor shock are chlorine combined with CYA, so they add it as they dissolve. The stabilizer guide covers the ranges and how to lower it.

Salt

Salt only matters if you have a salt chlorine generator. The MAHC tells public pools to keep salt “in the required range specified by the manufacturer,” and the makers’ numbers in Chart 2 differ.

Saturation index

The saturation index combines pH, temperature, calcium hardness, alkalinity and dissolved solids into one balance number. Hayward says water is balanced at “0 ±.2”; below −0.2 “the water is corrosive and plaster pool walls will be dissolved,” and above +0.2 “scaling and staining will occur.” CircuPool adds that a high index can cause “excessive calcium scaling on the salt cell.”

How often to test

CDC’s advice for home pools is direct: “Test chlorine concentration and pH at least twice per day, and more often when the pool or hot tub is being used by a number of people.” CDC recommends a DPD test kit for the most accurate results and notes that test strips “are less accurate.”

For public pools, the MAHC requires total alkalinity tests weekly and calcium hardness and CYA tests monthly. The test kit list compares kits that cover these readings.

If you use bromine instead of chlorine, the numbers are different. See the bromine vs chlorine comparison .

Sources

• CDC: Home Pool and Hot Tub Water Treatment and Testing
• CDC: Use Pool Chemicals Safely poster
• CDC: 2024 Model Aquatic Health Code and annex
• Pentair IntelliChlor Plus and LT installation and user’s guide (PHTA table)
• Hayward AquaRite owner’s manual
• CircuPool CORE Series manual

Facts were checked against these sources on October 9, 2026. This guide summarizes published guidance and labels; it is not based on hands-on testing.

FAQ

What are the ideal pool chemical levels?

It depends on the source. CDC recommends pH 7.0 to 7.8 and at least 1 ppm free chlorine, or 2 ppm with stabilizer. The PHTA table in Pentair’s manual gives free chlorine 2 to 4 ppm, pH 7.4 to 7.6, alkalinity 80 to 120 ppm, calcium hardness 200 to 400 ppm and stabilizer 0 to 50 ppm. Salt systems add a salt target from their manual.

What is the difference between free and combined chlorine?

Free chlorine is the part available to disinfect. Combined chlorine is chlorine tied up as chloramines, which the MAHC says are less reactive. The MAHC calculates it as total chlorine minus free chlorine.

How often should I test my pool water?

CDC says to test chlorine and pH at least twice a day, and more often when many people are using the pool. For public pools, the MAHC requires alkalinity weekly and calcium hardness monthly.

Why do pool chemistry charts disagree?

They are written for different purposes. The MAHC sets limits for public pools, PHTA publishes recommended ranges, and salt-system makers set ranges that suit their equipment. Where they differ, follow your equipment manual and product labels.