How to Use a Pool Test Kit: The Right Way to Check Water Quality

pool cleaning supplies
Pool cleaning and testing supplies. Getty Images
  • 01 of 10

    Before You Begin

    Pool test kit
    Pool test kit. Raymond Forbes/Getty Images

    The sun has been shining more intensely and flowers are blooming. Soon, it will be backyard swim party and barbecue weather. That means it's time to use some sort of pool test kit to check levels and water quality. Don't panic if you didn't ace chemistry in school—the kit is fairly easy to use if you just follow the directions.This particular kit, the 4-in-1 by Guardex, tests your pool water's pH, total chlorine, total bromine, acid demand, and total alkalinity.

    Other types of...MORE kits include test strips or provide an analysis through the manufacturer's website, an app or online calculator, or by taking the kit to your pool supply store. Be aware that the bottle numbers, vial sizes, and chemicals in this tutorial are unique to this particular brand of test kit. Follow the instructions for your own kit; usually, you can find them online.


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  • 02 of 10

    Just Dip it

    dip the test kit in the water
    Dip the plastic tester beneath the surface. Lisa Hallett Taylor

    Dip the plastic tester into your pool, making sure you draw water from a depth of at least 18 inches for an accurate "catch."


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  • 03 of 10

    Fill to "Fill"

    fill up to line
    Fill up to the line with pool water. Lisa Hallett Taylor

    Fill the small vial to the "fill" line with a sample of the pool water.


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  • 04 of 10

    Testing Free Chlorine and Chlorine Residual

    pool test kit
    Add five drops of a chlorine indicator. Lisa Hallett Taylor

    Add five drops of solution No. 1, which, in this kit, happens to be ortho-Tolidin, a chlorine indicator.


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  • 05 of 10

    Cap the Vials

    pool test kit
    Cap securely and invert. Lisa Hallett Taylor

    Place caps on vials and slowly invert or turn upside down several times.


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  • 06 of 10

    Color Comparison

    pool test kit
    Compare colors for chlorine residual level. Lisa Hallett Taylor

    Wait a few seconds to compare the color in the vial with the color standards indicated on the plastic tester to determine the free chlorine level. After that, wait a couple minutes and compare again to determine the chlorine residual level. Again, check the instructions or test kit website if you aren't sure what to do.


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  • 07 of 10

    Testing the Pool's pH Levels

    phenol red
    Add five drops of phenol red indicator. Lisa Hallett Taylor

    Fill the large tube to the top solid line with pool water from a depth of 18 inches. Add one drop of solution No. 4 and mix by gently swirling. This solution is sodium thiosulfate, a chlorine neutralizer. Add five drops of Solution 2, a phenol red indicator, and mix by gently swirling. Compare the color with the pH color standards on the plastic tester. Warning: don’t perform this test if the chlorine residual is above 3.0.


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  • 08 of 10

    Acid Demand Test

    Add the acid demand titrant. Lisa Hallett Taylor

    Using a sample from the pH test, add the acid demand titrant. Count each drop—making sure to swirl between drops—until the color matches that of the 7.4 indicator. Refer to the acid dosage chart for the correct amount of acid to add to your pool. Warning: don’t perform this test if the pH is above 7.5 and the chlorine residual is above 3.0.


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  • 09 of 10

    Testing for Total Alkalinity

    pool test kit
    Check color changes. Lisa Hallett Taylor

    Fill the large tube to the lower dash line. Add one drop of No. 4 and swirl. Next, add one drop of solution No. 5B, a total alkalinity indicator, and swirl. Add No. 3 (count and write down or remember each drop and swirl) until the color changes to clear, light yellow, or light green. Finally, multiply the number of drops of solution No. 3 you used by 10 to determine the total alkalinity. If multiplication makes you uncomfortable, use your smart phone's calculator. Warning: don't perform...MORE this test if the chlorine residual is above 3.0.


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  • 10 of 10

    Rinse and Dry

    pool cleaning supplies
    Pool cleaning and testing supplies. Getty Images

    After testing, rinse your plastic tester in a sink (never in the pool), dry, pack up the kit and put it in a cool, dry place, up high away from little hands. Some experts suggest using your test kit weekly during the swimming season.

    Don’t buy more pool chemicals than you’ll use in a season, because they can lose effectiveness over time.