Ditto. Sodium percarbonate is best used for getting rid of Baquacil/biguanide/PHMB if one wants the conversion to go faster and be less colorful than using chlorine alone to do the job. However, it costs more than using chlorine for that purpose.

Basically, sodium percarbonate is equivalent to adding sodium carbonate (i.e. "pH Up") and hydrogen peroxide with the latter being completely incompatible with chlorine (i.e. the two will annihilate each other...gently).