No Chlorine

[chem geek]

You can always do a bucket test to see how much chlorine it will take before it starts to hold. Take a bucket of pool water and add chlorinating liquid or 6% bleach to it and then stir it up and measure the FC and CC level after a few minutes. You might also test for ammonia before you get started with this (you can test for ammonia using an inexpensive test kit from a fish/pet/aquarium store). 1 teaspoon of 6% bleach in 2 gallons of pool water would be around 40 ppm FC.

Phosphates are not the issue here and you will continue to waste your money if you keep going down that path. You can learn more by reading the Pool School.