I switched my tub over to a SWG on 7-8-12. I never have shocked it, just added a few ounce of bleach and added the SWG and have maintained a 3-4 ppm chlorine level. As far as I can tell, it has never been below 2 ppm, usually 3-5 ppm. My tub is 395 gallons and the water is crystal clear. I have...