What is the recommended free available chlorine level for spa/hot tubs?

• A. 1-2 mg/L
• B. 2-5 mg/L
• C. 5-10 mg/L
• D. 0 mg/L

Answer: (B)

Keeping a free chlorine residual in spa water is about balance: the water must stay sanitary in a hot, high-bather-load environment, but the sanitizer should not irritate users. Spas are heated, which speeds chlorine loss, so a moderate residual is needed to maintain disinfection between tests. The two to five milligrams per liter range provides enough sanitizer to control microbes while avoiding the strong odor and irritation that come with higher levels. Going lower can leave the water under-chlorinated after use, while going much higher increases skin/eye irritation and can be harsh on equipment. So, the recommended level is two to five mg/L.