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In Depth Guide On How to Use a Pool Test Kit

March 11, 2021

Summer is approaching and pool season is upon us. It is time to check your pool and make sure it's in top notch condition. To ensure such condition, we recommended to do a routine pool testing for pH, chlorine levels, total alkalinity and acid demand to name a few pool tests. But how are these tests done? You don’t have to worry, these tests are easy to do because there are many pool test kits available in the market and it doesn’t require you to be an expert in chemistry to use. In this article, we will guide you through how to use a pool test kit to have that nice and clean pool this season.

Most backyard pools use standard pool test kits and there are several standard test kits for you to use in order to know the levels of the chemical in your pool. They can be a 2-in-1 (pH and chlorine), 4-in-1 (pH, chlorine, acid demand, alkalinity), 5-in-1 (pH, chlorine, bromine, alkalinity, acid demand), 6-in-1 (pH, chlorine, bromine, total hardness, alkalinity and cyanuric acid).  Choosing one can be based on what you want to test and what chemicals you are putting in your pool.

Though these standard test kits can test your pool for several principal tests that most pool owners need, there are special tests that can be conducted for certain conditions and here are some examples;

  • Salt test strip - used on salt water pool to test for salt and chlorine especially if you are using a salt-chlorine generator.
  • Phosphate test strip - used to test phosphates which comes from organic materials such as dead leaves and lawn fertilizers. Increased phosphate levels in your pool can lead to algae build-up since they feed on phosphates.
  • DPD test - this test can be used to determine chloramine levels which comes from free chlorine combined with ammonia. Increased chloramine in your pool can be identified by the strong smell of chlorine and can be corrected with shocks to remove the chloramine.
  • SafeDip Test Meter - tests your pool water for the total dissolved solids.
  • Biguanide Water Treatment System - uses biguanide test strips to measure sanitizer levels, pH, alkalinity, and calcium hardness levels.

How To Test Your Pool Water Using a Pool Test Kit

As mentioned earlier you don’t have to be an expert in chemistry to conduct this testing. And the process is pretty simple. Here are the steps on using a standard pool test kit (Four-way pool water test kit).

Getting the Sample

Dip your pool tester into your pool. We recommend you dip your tester at least 18 inches into your pool to have an accurate result because the water chemistry near the surface can be different compared to the deeper part of your pool.

Testing the Chlorine Level

After making sure that the vials are filled up to the marked fill line, add 5 drops of solution No.1 (ortho-Toluidine) into the smaller vial for testing chlorine. While in this test we used a liquid testing solution, some testing kits use tablets instead of a liquid tester.

Mix the water and the ortho-Toluidine indicator solution thoroughly by turning the vial upside down after putting the cap. After a few seconds, compare the color in the vial with the standard indicator on the tester to see the current free chlorine level. To determine the residual chlorine level, you must wait for a few minutes and compare the color again with the indicators on the tester.

Testing the pH Level

On the larger vial, add a drop of the No. 4 solution (sodium thiosulfate) and five drops of No. 2 solution (phenol red). Then slowly mix the pool water solution. After a few seconds compare the color with the pH indicators on the tester.

Testing the Acid Demand

Using the same water from the pH test, Add drops of the acid demand titrant while swirling in between drops until the water color matches the 7.4 pH indicator.

Testing the Alkalinity

Rinse the tester, then fill the larger tube up to the alkalinity line. After that add a drop of the No. 4 solution and mix. Then add a drop of No.5B solution, this is the alkalinity indicator, and mix the solution. Lastly, count the drops as you add the No.3 solution until the water becomes clear, light yellow or light green in color. Then you will multiply the number of drops of No. 3 solution you added by ten to calculate the total alkalinity of your pool.

Here is a video of the procedure:

Considerations When Conducting the Test

  • Though in this testing kit the chlorine test included both free and residual chlorine test, some testing kits may have two separate tests for these and it may also use different solutions or tablets
  • Residual chlorine should be adjusted to normal levels in order to continue the following test; acid demand, pH level and total alkalinity. Residual chlorine levels above 3.0 should be corrected in order to have an accurate result.
  • If the pH is above 7.5, the acid demand should not be conducted since it will produce an inaccurate result.
  • After the tests make sure you clean and rinse the tester in your sink. Do not rinse it on your pool because it may cause an imbalance to your pool’s chemistry.
  • Make sure that the testing kit is stored in a cool dry place and away from children to avoid poisoning.

How Often Should You Test Your Pool Water?

The time for pool testing can vary from owner to owner. They could be weekly, monthly or even daily, though this might be too much, depending on how often you want to test your pool. But based on our experience and according to most pool experts testing for the following should be;

  • Chlorine level testing - two to three times a week
  • pH testing - two to three times a week
  • Total alkalinity - weekly is preferred but if you pool’s pH has changed during your pH testing we would recommend that a total alkalinity test should be done.
  • Acid demand test - every time your pool needs a pH adjustment and acid demand test should be done.
  • Calcium hardness - once a month
  • Cyanuric acid levels - once a month
  • Total dissolved solids - once a month

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