Scale formation in your hot tub is common in areas subject to hard water. High alkaline levels in the water supply cause scale deposits to settle onto the surface of the hot tub, creating unattractive stains. Scale can also build up within the hot tub jets, causing the jets to run more slowly or to blow dark flaky particles into the hot tub. This makes it important to remove the scale the right way.
Turn on the hot water supply to the hot tub, and put in the plug so the water does not drain.
Pour 2 cups vinegar and 3 tbsp. of powdered dishwasher detergent into the hot tub.
Turn the jets on high, and let the hot tub run for 30 minutes. The pressure from the jets will create a powerful water flow that will flush out the jets plus clean the surface of the hot tub. The detergent will assist in breaking up the scale, and the vinegar will dissolve the scale.
Drain the tub.
Refill the tub with plain hot water, turn on high and let run for 15 minutes.
Drain once more, and the tub is now scale-free and ready for use.