Calcium deposits are a common problem when it comes to hot tubs. The buildup develops as flaky chunks that end up floating around in the water as you soak. The main issue is the mineral content that settles into your jet lines, which later pushes out when you turn the jets back on and creates those chunks of residue. To remove, use a few household ingredients that break apart the buildup.
Make sure the water in the hot tub is above all jet line openings.
Pour 1 cup bleach and 1/2 cup dishwasher detergent into the hot tub and turn the jets on high.
Let the jets run for 15 minutes and drain the tub.
Refill the hot tub with plain hot water and run the jets another 15 minutes to flush out the jets once more.
Drain the hot tub again and refill when it's ready for use.