Spa water has strong chemical or musty odor despite normal readings

Safety first: Avoid using the spa until water quality is restored; contaminated water can cause skin and respiratory irritation.

• Test water: Use a reliable test kit to check free chlorine/bromine, pH, alkalinity, and combined chlorine.
• Shock treatment: Add a non-chlorine shock or chlorine shock per Master Spas water care guidelines to oxidize contaminants.
• Clean filters: Remove and deep-clean or replace filters to remove trapped organics.
• Run pumps: Run all pumps and water features to circulate shock through all plumbing.
• Check ozone/UV: Verify that the ozone generator and/or UV system are operating if your spa is equipped with them.
• Drain and refill: If odor persists, perform a plumbing purge with a spa line cleaner, then drain, clean shell, replace filters, and refill with fresh water.