Clorox® Pool&Spa Swimming Pool Shock XTRABLUE® Plus™ Granules, Kills Bacteria & Algae in Swimming Pools, Swim-Ready in 15 Minutes, (12-Pack)

I use these in my 13,500 gallon round above ground pool, one bag per treatment. Sodium dichloro-s-triazinetrione with 72% dihydrate, 28% triazinetrione w/ 40% Chlorine. I also run the Intex 26651EG 3,000 GPH Above Ground Pool Sand Filter Pump with Automatic Timer where I occasionally add half the prescribed SHOCK directly to the Filter Skimmer attachment in order to clean / sanitize the sand in the filter. During the sunny months I might have to use XtraBlue SHOCK once a week and I've found this formula to be the best for longevity of my Vinyl Liner and also allowing swimming later the same day, or the next day. I ALWAYS dissolve the powder in a five gallon tool bucket first then distribute the dissolved XtraBlue SHOCK around the pool perimeter and center, and a splash some directly into the Sand Filter. It dissolves quickly and easily. The pool has been up and running 24/7/365 for five years now with zero water issues. Well, one water issue about two years ago where Cyanuric Acid got too high, and draining 1/3 (one third, about 500 gallons) and refilling was the only solution. I highly recommend this XtraBlue SHOCK for the usage I've described. Use Formula; Sodium dichloro-s-triazinetrione with 72% dihydrate, 28% triazinetrione w/ 40% Chlorine.