Test kits for PP use the Chlorine test procedure and adjust the value based on the oxidation value. A value of 4.0ppm of chlorine with a pool test kit will translate to a value of 3ppm PP. I will try to maintain my PP level at a chlorine level of 3 ppm for the treatment time, assuring the treatment lasts. If you are doing the treatment and then neutralizing the treatment with dechlor or hp, then residuals of those will neutralize the next days treatment.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard