With over 40 years of experience, we are here to share our Pool, Hot Tub & Hearth advice.

Water Testing for Saltwater Pools

Saltwater pools use a chlorine generator with an electrolytic cell, which produces chlorine as the salt passes over the cell. You’ll add several 50-pound bags of salt a few times a year.

The ocean contains about 35,000 ppm of salt (3.5 percent), while a saltwater pool is kept at 3,000 ppm. Your eyes, skin, and tongue shouldn’t be able to detect the salt at all. Since salt is a natural conditioner, your skin will actually feel smoother, and your eyes won’t be irritated.

Because the chlorine from a salt chlorine generator is pure and is not combined with additives found in solid products, this form of chlorination does not affect total alkalinity or calcium hardness directly.

Heavy swimmer load like a “Pool Party”, rain and windborne contaminants, splash-out, carryout, and treatment chemicals all affect these levels. Free chlorine, Total Alkalinity and pH should be checked weekly and Calcium Hardness be tested at least monthly.

As water is recycled through the salt chlorine generator, any combined chlorine—the irritant that causes red eyes and the unmistakable chlorine odor is eliminated as it passes over the electrolytic cell. Under normal conditions, there should be little combined chlorine in a pool with a salt chlorine generator. But after a pool party, heavy rain or windstorms, or if there are signs of an algae bloom, test for combined chlorine.

If the combined chlorine level exceeds 0.2 ppm, you will need to super chlorinate the water. Some salt chlorine generators are equipped with a “boost feature” that enables you to increase the chlorine level over a short period of time (usually within 24 hours). Or, use the traditional method of “shocking your pool” and add more chlorine directly to the water yourself.

After super chlorinating/shocking, the chlorine level should be tested again before the pool is reopened to swimmers. EPA guidelines suggest 4 ppm is a safe re-entry level.

pH is influenced by the total alkalinity of the water. When adjusted to within the recommended range of 80–120 ppm, total alkalinity acts as a buffer for pH. Read your chlorine generator manual; some manufacturer’s recommend the generator tends to keep a steadier pH with an alkalinity between 90–100 ppm.

A pH outside of the acceptable range (7.2–7.8, ideally 7.4–7.6) is potentially irritating to bathers. When pH is too high, chlorine’s sanitizing ability is lessened and scale tends to form on pool surfaces and equipment. When pH is too low the water tends to be corrosive, pitting the concrete and dissolving the metal it touches.

When the calcium hardness level is too low, water can become aggressive even if the pH is within the recommended range. It may damage plaster, concrete, and grout and could lead to equipment corrosion.

A high calcium hardness level causes the water to deposit scale, also regardless of pH. This crusty build-up is unsightly and rough to the touch. Deposits can clog filters and piping as well as cause heaters to fail.

Chlorine Stabilizer
An outdoor pool being chlorinated with salt water will require the addition of cyanuric acid “stabilizer” to slow the rate UV rays in sunlight destroy the free chlorine residual. (The range recommended by the International Aquatic Foundation is 30–50 ppm). It is particularly important to test the cyanuric acid level regularly during the summer months when the sun’s rays are strongest.

Balanced water, correct salt and stabilizer levels will extend the life of the chlorinator and provide you with the best possible swimming experience.