This year our pool was perfect in the beginning. Salt water 10,000 gal
Then the salt generator was flashing high chlorine. Got that down with back wash added hose water and phos free. Took a couple weeks before it went down algae showed up on walls. Used algecide and when it rained added more phos free. I used stain and scale once or twice a week in between. More algecide as smaller does didnt work. Now chlorine generator flashing high chlorine again! Used phos free again after another rain. Chlor level good again. Frustrated. Also wondering what are chances the water could cause intestinal trouble?
Then the salt generator was flashing high chlorine. Got that down with back wash added hose water and phos free. Took a couple weeks before it went down algae showed up on walls. Used algecide and when it rained added more phos free. I used stain and scale once or twice a week in between. More algecide as smaller does didnt work. Now chlorine generator flashing high chlorine again! Used phos free again after another rain. Chlor level good again. Frustrated. Also wondering what are chances the water could cause intestinal trouble?
I can tell already from your numerous attempt to use Phos-Free that the pool store is pulling one over you and happily taking your money. 
Please feel free to start anew thread in the sub-forum below about your water and we'll get you taken care of. It's not hard with the proper test kit and some basic knowledge.