We have customer loyalty programs when it comes to watercare stuff. Perhaps your dealer does too?
I know some dealers are still the old pencil and pen, but I've stated here before and so has a couple other posters. Support your dealer, and they can better support you. I gave an example of a cover replacement. I had on record because I use the best (which still sucks) software program for the pool and spa industry called Evosus. It allows me to easily pull everyones previous purchases. Even though the cover was waterlogged, and well outside warranty, I could see that they purchased their 303 aerospace protectant as well as all water treatment care from me.
I brought that information to customer service at the various vendor, and they agreed to ship me a new cover for free for my customer.
You buy your stuff online, it doesn't hurt the dealer as much. Margin on watercare isn't great since we do try to compete with guys living in their moms basement with no overhead. However, it could hurt you if you need someone to go the extra mile later in your hot tub life
At least... if I am your dealer