How to Use a Pool Test Kit to Check Water Quality

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  • 01 of 10

    Before You Begin

    A pool test kit
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    The beginning of warm weather means the beginning of pool season! That's when it's time to check your water levels and water quality. Don't panic if you didn't ace chemistry in school—pool test kits are fairly easy to use if you 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 kits include test strips or provide 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 kit; usually, you can find them online.


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  • 02 of 10

    Just Dip it

    Dip the test kit in the water
    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"

    A pool test kit filled up to the line
    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

    A pool test kit testing chlorine
    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

    A pool test kit filled, with capped vials
    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

    A pool test kit with a color comparison
    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 of 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

    A pool test kit adding phenol red to test pH
    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. Whatever you do, don’t perform this test if the chlorine residual is above 3.0.


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  • 08 of 10

    Acid Demand Test

    A pool test's acid demand test
    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 indicators. Refer to the acid dosage chart for the correct amount of acid to add to your pool. Whatever you do, 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

    A pool test kit total alkalinity portion
    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. Whatever you do, don't perform this test if the chlorine residual is above 3.0.


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  • 10 of 10

    Rinse and Dry

    pool cleaning 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.