Measure free chlorine, pH value and alkalinity of swimming pools or spa easily with 3-in-1 Pond Test Strips from Pool Improve. It is very simple and easy to use. You just need to immerse the test strips into the water for a few seconds. Then remove it and wait for a moment, compare the colour change to get the result of the water quality. With the test result, you will know what chemicals need to be adjusted to keep a spa or pool water clean and clear.