SPECIAL CLEANING CONSIDERATIONS FOR HOT TUBS. Like all appliances, hot tubs require periodic maintenance. Remember, while soaking in what seems like a perfectly clean hot tub, behind the scenes, there are many feet of interior plumbing lines moving water seamlessly throughout the spa to dozens of jets. When not in use these plumbing lines become an area of buildup from non-living nutrients such as lotions, sunscreens, cosmetics, sweat and other gunk. No matter how diligent you are about maintaining your portable hot tub, over time, it will likely develop gunk in the plumbing system. It’s a natural occurrence common with any closed-loop warm water vessel like portable spas. IT'S ALL ABOUT TEMPERATURE. Most hot tubs are heated between 98 and 104 degrees creating a wonderful soak but can have unintended consequences. We highly recommend you complete an Ouster treatment, drain spa and refill with fresh water if you experience any of these poor water quality symptoms. 1) You see black, gray, or white flakes, or gunk in the water, filters or shell surface. 2) There's a noticeable odor. 3) Your hot tub water is cloudy on a regular basis. 4) You are buying chemicals more frequently or using more on a weekly basis to maintain good water quality. 5) Your skin itches after you exit the hot tub. 6) Your hot tub is older than 1-year or it was purchased used. PURGE HOT TUB 2-3 TIMES A YEAR. Portable spas should be periodically “cleaned inside out” regardless of the daily watercare regimen used. Ouster Hot Tub cleaner is specifically formulated to 'scrape' the interior pipes in your portable hot tub. It can reduce the gunk while keeping your plumbing jets clean and odor free with just one treatment every 3-4 months.