LaMotte Cyanuric Acid Test Kit, 6838

The LaMotte 6838 is a cyanuric acid test kit, the tool for checking the stabilizer level in a pool. It reads at 20, 30, 40, 50, 60, 80 and 100 ppm.

How the test runs

Fill the test tube with pool water, add one of the cyanuric acid TesTabs tablets and let it break up. The sample clouds as it does. You then look straight down through the tube and note the level at which the dot in the base of the tube stops being visible. That is the reading. The kit comes with 50 tablets, so it covers a long stretch of routine testing.

Why the number matters

Cyanuric acid protects free chlorine from ultraviolet light. Run it too low and sunlight strips the chlorine out of the water within hours. Run it too high and the chlorine that is there becomes sluggish, so the pool needs more of it to hold the same sanitizing power. Since stabilizer only leaves the water through dilution, it climbs quietly over a season and is worth measuring rather than assuming.