Using a Pool Test Kit to Check Water Quality

Project Overview

Total Time: 30 mins.
Skill Level: Beginner
Estimated Cost: $20

Warm weather equals pool season!
That’s when it is time to check your water quality.

In a typical home swimming pool, this means routinely checking:

  • pH
  • Chlorine
  • Total alkalinity
  • Acid demand

If you do not love chemistry, don’t worry; pool water testing kits are fairly easy to use if you follow the directions.

Working with Test Kits
Standard water chemistry tests come in several different types. The kit used for this demonstration, tests the pool water’s pH, chlorine, acid demand, and overall alkalinity. Other kits are the 2-in-1 (chlorine and pH); 5-in-1 (chlorine, bromine, alkalinity, pH, and acid demand); and 6-in-1 (chlorine, bromine, pH, total alkalinity, total hardness, and cyanuric acid).
Other kit types include testing strips or provide a breakdown through the manufacturer’s website, an app, or an online calculator. Taking a pool water sample by a pool supply store is another option. If testing your own water, always be sure to follow the instructions for your kit; which can typically be found online.

When to Test Pool Water
There is no set schedule for testing your pool water’s chemistry. Some people test daily, weekly, or even monthly and this is a perfectly acceptable. However, many pool professionals suggest the following schedule for testing:

What You’ll Need

Equipment / Tools

  • Four-way pool water test kit
  • Sink to wash test kit
  • Towel to dry test kit


  • Pool water sample

Tips for Testing Pool Water

  • Discoloration on the walls of a pool often indicates the presence of algae, which requires more frequent testing and super-chlorinating (shocking) the pool.
  • Don’t buy more pool chemicals than you’ll use in a season because they can lose effectiveness over time. Test solutions (reagents) typically last around a year. ​​
  • When you run out of testing solutions, you can purchase replenishment bottles rather than buying an entire testing kit. 
  • ​Testing kits are available that offer the testing solutions and materials required for nearly any chemical test you may need. These deluxe kits typically cost between $30 and $60.​


Take a Water Sample

Dunk the tester into the pool, making sure you collect water from a depth of 18 inches or more for an accurate “catch.” Surface water chemistry may differ from that which is deeper in the pool.

Check the Vial Levels
Double check that the vials are filled to the marked “fill” line on the column. Accurate readings require a specific ratio of pool water to the testing solution.
Test for Free Chlorine and Residual Chlorine
In our kit, five drops of solution (ortho-Tolidin) are added to the column for testing chlorine.
Note: Some test kits use dissolving tablets rather than a liquid testing solution.
Mix the Solution

Cap the vials, and turn them upside down several times to mix the solution with the pool water.

Compare the Colors
Wait a few moments, and compare the color in the vial with the color values shown on the tester. This will provide a reading of the free chlorine level.
Wait a couple of moments, and compare the colors again to verify the residual chlorine level.
Note: Some kits have separate tests for free chlorine and residual chlorine, each requiring different solutions or tablets. ​
Test the Pool’s pH Levels
After cleaning the tester, fill the large tube to the top solid line with pool water taken from a depth of at least 18 inches. Add one drop of sodium thiosulfate (a chlorine neutralizer) and mix it by swirling the tube. This solution is sodium thiosulfate, a chlorine neutralizer. Add five drops of a phenol red indicator solution, and mix by swirling the tube. Compare the color with the pH color values on the plastic tester to determine the pH level of your pool water.
Note: Do not do this test if the residual chlorine is above 3.0, as an accurate pH reading will not be achieved. Residual chlorine levels must be adjusted to normal prior to this test.
Test for Acid Demand
Using a sample of the water taken from the pH test, add the acid demand titrant. Count each drop, making sure to swirl between each one, until the color matches the value of the 7.4 indicator. Consult the acid dosage chart to verify the correct amount of acid to add to your pool to balance the pH.
Note: Do not perform this test if the pH is above 7.5 and the chlorine residual is above 3.0. Chlorine levels must be the proper level prior to testing the acid demand.
Test for Total Alkalinity
After cleaning the tester, fill the large tube to the lower dash line. Add one drop of sodium thiosulfate and swirl. Next, add one drop of a total alkalinity indicator solution, and swirl. Add titrant reagent solution, drop by drop (make sure to keep track) until the color changes to clear, light yellow, or light green.
Finally, multiply the number of titrant reagent solution drops you used by 10 to reveal the total alkalinity.
Note: Do not perform this test if residual chlorine is above 3.0. Chlorine must fall within the normal range prior to testing TA (total alkalinity).
Rinse and Dry the Tester

After testing is complete, rinse clean the plastic tester in a sink (never in the pool), then dry it completely. Store the kit in a cool, dry place, away from children.