Ozone indicator is on but no bubbles are visible from the ozone injector.

Safety first: Turn off power at the GFCI breaker before handling ozone equipment.

• Inspect tubing: Follow the clear ozone tubing from the ozonator to the injector. Look for kinks, cracks, or disconnections.
• Check check valve: Locate the ozone check valve in the tubing and ensure it is oriented correctly (arrow toward the spa). Replace if it is stuck or allows water to backflow.
• Clean or replace injector: The Mazzei injector can clog with scale. Remove it from the plumbing and soak in a descaling solution, or replace with a Marquis-compatible injector.
• Test ozonator output: Many modern ozonators have an indicator light. If the light is off or the unit is older than 3–5 years, replacement is recommended.