I'd be willing to bet that the "we'll come out to your pool and evaluate it" will result in suggestions (possibly quite insistent) for chems that will cost alot more than the K-2006. Maybe I'm wrong (and this site is an exception) but there's not alot of altruism in the pool biz, and probably none in a "free service" that's baked into a corporate operating procedure.

I also seriously doubt that the water changes much in 20 minutes.