i have a 18,000 gal. vinyl pool. last fall my cyanuric acid count was about 45ppm. i opened my pool this spring and tested my water for cyanuirc acid was 0ppm. i was wondering because i live in iowa if you could lose acid because of winter conditions or is it normal to lose it. i do drain about 6000 gals. out in the fall, then i get this back be cause of snow melt and rain that goes through my meyco safety cover. hope for an answer. thankyou Richard