- Add sample of water to test vial, filling to 10 mL mark.
- Add one No. 1 tablet, and crush to disintegrate the tablet.
- Fill the direct reading titrator with No. 2 solution. Be sure there are no air bubbles trapped in the titrator. Adjust so that the solution level coincides with the zero mark.
- Insert the titrator through the hole in the cap of the test vial.
- Gently depress the plunger on the titrator, adding the solution a drop at a time and swirling the tube gently to ensure mixing.
- Continue adding the solution until the color changes from green to purple.
- Observe the mark corresponding to the solution in the titrator. This figure represents the active sequest-test concentration in the sample as parts per million (ppm).
The results of this test are expressed in terms of ppm active sequestering agent. Commercially available products are normally sold as aqueous formulations with a given active sequestering agent content. To calculate the dosage of commercial products required from the test results, regard must be made of the active content of the product in use.
For most accurate results it is recommended that a blank be carried out on the water without sequestering agent compound, or on the makeup water to the system and the result of this test subtracted from the test reading obtained with the swimming pool water. Substances reported to interfere with this test are aluminum, polyphosphate, chelating agents and iron in high concentrations.
Ideal levels for chlorinated pools should be 10-12 ppm for maintenance and 18-20 ppm during stain removal. This test should be run on a regular basis to insure adequate levels of protection.
