You definitely need CYA in the pool with a SWCG. At about 60-80 ppm for most pools. The reason is the cell produces a high instantaneous chlorine concentration and a fair amount is immediately used in destroying the chloramines in the water at the cell. The CYA prevents the remaining chlorine from being used up until it gets into the pool itself.

I think that is what Poolsean or Mark mentioned but I may be corrected.

Pat