I would just add that with an SWG system, especially for an outdoor pool exposed to sunlight, it is very, very unlikely you will ever need to shock your pool. You will probably never see a combined chlorine level above 0.2 ppm (the smallest measurable amount with the Taylor test) except right after a heavy bather load and even then the combined chlorine should be eliminated within 24 hours.

The only time you would probably have to shock the pool would be after an "accident" (urinary or fecal). And as Sean says, you can just use chlorine for that.

Richard