Spa water has a musty or moldy odor, sometimes with slimy surfaces.

Safety first: Do not use the spa until the water is sanitized and odor-free.

• Shock heavily: Add a high dose of chlorine or non-chlorine shock according to label directions to kill bacteria.
• Clean cover: Remove the cover and clean both sides with a mild disinfectant safe for vinyl, then rinse thoroughly.
• Use pipe cleaner: Before the next drain, circulate a spa pipe and jet cleaner through the system to remove biofilm from plumbing.
• Drain and refill: After treatment, drain the spa completely, wipe all surfaces, refill with fresh water, and rebalance chemicals.

Maintain proper sanitizer levels and regular water changes to prevent recurrence.