You'll spend a whole lot less if you'll stay out of that pool store. There is no such thing as "chlorine lock"--rather, you shock your pool to the chlorine level that is determined by your CYA level (see the link to the best guess chlorine chart in Watermom's sig for more information on that). You can shock the pool with plain, unscented bleach for a whole lot less than you paid for the "burnout", and without adding any extra goop to your pool to create more problems (if it's cal-hypo, you're adding unneeded calcium..if it's dichlor, you're pushing your pH way down and adding stabilizer.)