How to Use a Pool Water Test Kit

Kenneth Wilson

Knowing how to test for your pool water chemistry is an essential skill that every pool owner should have. This is the best way to avoid common water quality problems and make sure that your pool water is always safe to swim in.

But before we discuss how to do it, here’s a list of the basic components you need to test for. 

For homeowners,
it is important to regularly check for:

  • pH level
  • Chlorine levels
  • Acid demand
  • Total Alkalinity
  • Aside from these four, some pool owners or commercial pools test for:

    • Total Hardness
    • Calcium Hardness
    • Cyanuric Acid Levels
    • Total Dissolved Solids or TDS
    • Bromine

    How To Test your Pool Water Chemistry

    Before we begin, you must first be aware that how to test your pool water chemistry differs for each brand. Some have included test strips, works with an app, has an online calculator, or offer manufacturer’s analysis through their website. The vial size, bottle numbers, and chemicals also differ per product, so it’s best to follow the manufacturer’s instructions - which usually comes with the box or can be found online. They may differ but it's minimal since they tend to work similarly.

    For this post, I’ll share with you a pool water test kit that can determine the four basic components: pH, chlorine, acid demand, and alkalinity. This product contains a testing vial and reagents or testing agents.

    Note: The reagents, also known as testing agents or solution, have a shelf life of only one year. Don't worry, you can purchase them individually. 

    1. Get a sample

    When getting a sample, make sure to get pool water from 12 to 18 inches (30 to 46 centimeters), or one elbow below the pool surface. Make sure that the water reaches the high range or fill line.

    2. Add reagent to the vials

    To test the chlorine, you have to put five drops of reagent bottle no. 1 in the small or chlorine vial. 

    For the bigger or pH vial, you will need to put one drop of reagent no. 4, which is a chlorine neutralizer. It is important to neutralize chlorine because if it is too high, it will affect your pH test and provide the wrong readings. After, add five drops of reagent no. 2.

    3. Place the cap on the vials and read the results

    You need to place the cap on the vial so you can mix the pool water sample and reagents. Never use your hands to cover the top to shake because our body contains oils that will affect the readings.

    You can now read the results - to see the reading clearly, add the white card located in your kit.

    4. Acid Demand Test

    For this test, you will need to use the content of the pH vial. This will help you determine how much acid you will need to add if the pH level is beyond 7.6. The number of adds you drop will vary per pool. Add one drop of reagent no. 3 and slowly mix the contents. Each drop should change the color and you will need to remember how many total drops you added until it changes to the color range of 7.4 to 7.6.

    Once it’s between that range, check the acid demand table located in the test kit. Find out how many gallons your pool is and then see how many pints of muriatic acid you will need based on the number of drops you added.

    Note: If you have added one to two drops of reagent no. 3 and the color dropped quickly to a lower pH level, you are having problems with alkalinity. It's best to find out your alkalinity level before adding acid to lower the pH level.

    5. Testing the Alkalinity

    Fill the bigger or pH vial until the alkalinity fill line. Add one to two drops of reagent no. 4 or chlorine neutralizer. Similar to testing a pH level, you also need to neutralize the chlorine since it may affect the reading as well. After, add two to three drops of reagent no. 5. Slowly swirl the vial to mix the contents so you don’t need to cover it. 

    For the last reagent, it will vary per pool. Add one drop of reagent no. 3 and then mix the contents. Do this repeatedly until the water clears.

    Make sure to remember how many drops of reagent no. 3 you added because you will need to multiply this by 10 to find out the alkalinity level.

    Example: 8 drops x 10 = 80 parts per million of alkalinity


    Most pool kits work similarly to this pool kit but the number of drops and bottle numbers will differ. Make sure to read and follow your product’s instructions to get the right readings.

    Note: You don’t need to buy a new test kit when you don’t have testing solutions anymore. Most brands sell replenishment bottles.

    What is the recommended level for each component?

    Your goal is to bring your basic components to: 

    Chlorine level: 1 part per million to 3 parts per million

    pH level: 7.4 to 7.6

    Alkalinity: 80 to 120 parts per million

    What happens when you’re outside the ideal level?

    If you have a low chlorine level, this may result in algae infestation and cause viral or bacterial infections. The chlorine level shouldn’t be too high as well because it will cause skin irritation, make your eyes burn, and bleach the pool.

    For the pH level, if it’s low, the water is acidic. The pool will become corrosive and damage your equipment and plaster as well as cause eye and skin irritation. When the pH level is too high, this will allow calcium to build-up on your pool tile lines and plumbing, and also irritate the eyes and skin.

    It is important to maintain your alkalinity level because this is the buffer for the pH. When it is low, the pH level is also low. Having high alkalinity also means you have a high pH level. You will have a hard time balancing your pH level if your alkalinity level is off.

    When should you test your pool water chemistry?

    When to test your pool depends on what component you’re checking for. Some people test their pool water every day, but you don’t have to follow the same schedule.

    It is recommended to check the pH and chlorine levels at least two to three times per week. For total alkalinity, once a week is fine, but if the pH level changes, you have to test it as well. You also need to check the acid demand when you need to adjust your pH levels. 

    For the other components, such as cyanuric acid levels, calcium hardness, and total dissolved solids, checking these once a month is enough.

    Kenneth Wilson
    November 12, 2019
    Ideas & Inspiration

    Kenneth Wilson

    Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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