When you have a hot tub, a line of scum and bacteria can often accumulate inside of the pipe drains and around the top water line of the hot tub. To clean scum from all parts of the hot tub simultaneously, use a cleaning solution that flushes the jet pipes and cleans the hot tub surface. You can do this with low-cost cleaning items that are probably already on hand.
Scrub the scum line around the top of the hot tub with a wet nylon-scrubbing pad. Sprinkle dishwasher detergent onto the pad and continue scrubbing until you remove most of or all of the residue. Using a dishwasher detergent is better than plain dish soap as it is a low-sudsing formula.
Pour 1/4 cup dishwasher detergent into the hot tub along with 1/2 cup bleach.
Turn the hot tub jets on high and let them run for 15 minutes.
Wipe down any remaining scum line around the top of the tub with the nylon-scrubbing pad and drain the tub.
Refill the tub with fresh water and run the jets for an extra 10 minutes to flush out any excess residue.