nice system you got there, and the constant water changes have other benefits as well besides CYA accumulation. no substitute for clean water thats for sure. You could even use straight bleach as well, target 50pmm CYA and do even better. Ive put in a dedicated, valved drain line that empties into a french drain, and wished for a dedicated hot water supply line... For those of us with portable spas and no convenient hot water supply nearby, the "dichlor then switch to bleach" method for CL spas, and pure bleach for bromine spas works really well to extend the drain interval just from standpoint of CYA moderating sanitizer strength. I get an additional boost from using the periodic serum watercare maintenance treatments as well.