I would add this:
To 'shock' a tub you need to put in your measured amount of chlorine (I add 2 dry ounces per 500 gallons) and run the jets with the lid open to let it gas off and not harm your cover.
BUT - you need to test the chlorine level again some time later to be SURE that you have accomplished your goal. For example, if you don't add as much as I do, OR if there is something alive in your tub besides you - you may come back six hours later, test, and find that there is NO measurable amount of chlorine in the water. That means you did not do a successful shock - the chlorine got just so far, and then was depleted.
So - add one more step to your regimen: after you shock, test the next day before use to be certain you have complete a successful shock.
HTH