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Pool Water Testing 101

Safe, healthy water. It’s what we all want most when it comes to our pools and spas.

Regularly testing your water is an essential part of maintaining your pool’s welfare. Getting an accurate reading of your water chemistry helps you understand exactly how much of what product your pool needs. Testing your pool water prevents the possibility of under-treating or over-treating the water, which keeps your pool properly balanced and saves you money!

Let’s go over a few of the basics when it comes to properly testing your pool’s water. There are two ways to test your pool water — at home or in-store.

At-Home Pool Water Testing

Leslie’s offers several options you can use at home, including test kits and test strips. Testing at home is easy, but there are a few things you need to know before getting started. Which type of test will work best for you? Let’s take a quick look at the pros and cons of each:

Liquid Test Kits


  • Most accurate type of water test. Liquid DPD reagents are the best for testing chlorine levels in your pool

  • Testing available for more diverse aspects of water chemistry

  • This method is used by pool professionals and health departments


  • Most expensive water test

  • Testing process can take longer and be more complicated than test strips

  • Reagent bottles must be held vertically to ensure uniform drop size, and drops must be counted as they’re slowly added

  • More prone to user-error

DIY TIP: Remember to never touch the reagent dropper tips, and always wash your hands after using water test reagents. Also make sure to never interchange reagent caps.


Test Strips


  • Fastest water test

  • Simple to use and read

  • Least expensive to purchase

  • Most popular option for pool owners wanting a quick, daily pool chemistry analysis


  • Fewer options for testing capabilities

  • Not as accurate or precise as a liquid test kit

  • Some results take just a few seconds to develop, and some take longer; for tests with multiple results on the same strip, it’s important to understand the timing so you don’t get inaccurate results

  • Hands must be completely dry when removing the strip from the container


General At-Home Testing Tips

It’s a good idea to always keep essential pool chemicals on hand so you can treat your pool as needed. These include a primary sanitizer to kill viruses and bacteria, a weekly shock to keep your sanitizer working effectively, and water balancers to manage pH, Total Alkalinity, and Calcium Hardness. Use the results of your water test and the size of your pool to determine proper dosage according to the product label. Here are 10 helpful tips to get the most accurate testing results:

  1. Always follow the instructions that are included with the test kit or test strips.

  2. Typical water tests include measurements for Free and Total Available Chlorine, pH, Total Alkalinity, Calcium Hardness, and Cyanuric Acid. If your pool has a salt system, the salt level should also be checked.

  3. For test kits, take your water sample from 12 to 18 inches below the surface after the circulation system has been on for an hour. A good rule of thumb is to take your water sample from about elbow deep in the pool water, away from the return fittings. For test strips, dip the strip per the label directions.

  4. Ideal testing ranges are as follows:

    • Free Available Chlorine: 2.0-4.0 ppm

    • pH: 7.4-7.6

    • Total Alkalinity: 80-120 ppm

    • Calcium Hardness: 200-400 ppm

    • Cyanuric Acid: 30-50 ppm

  5. High chlorine levels can skew other readings, such as pH and Total Alkalinity. If high levels of chlorine are present, a chlorine neutralizer can be added to the pool water. Some kits don’t recommend testing the pH and Total Alkalinity if the chlorine reading is 5.0 parts per million (ppm) or higher.

  6. It can take a moment for some testing reactions to occur. Familiarize yourself with the instructions before using any type of water test.

  7. Store all test materials in a cool, dark area, and check them for accuracy on a yearly basis. Expired testing materials can cause inaccurate readings.

  8. Water tests should always be completed before adding any chemicals.

  9. After adding chemicals, it’s important to let the water circulate completely before testing your water again. This process usually takes about 4-8 hours for most pools, but is the timing is dependent on the pump size, run time, and pool size. Always follow the product label directions to ensure adequate product circulation.

  10. Even if you test at home on a regular basis, we recommend taking a water sample to your local pool store at least once per month to ensure all aspects of your water are in their proper ranges.

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