Safety first: Turn off power at the GFCI breaker before opening the equipment bay or moving valves.

1. Clean or replace filter: Remove the filter and rinse thoroughly. If HFL clears with the filter removed, replace the filter with a new Sundance-compatible cartridge.
2. Check slice valves: Verify that all gate/slice valves around the circulation pump and heater are fully open and locked in the up position.
3. Bleed air from system: Loosen the union on the circulation pump or heater slightly until water flows steadily, then retighten. This removes trapped air that can reduce flow.
4. Inspect circulation pump: With power ON, confirm that the circulation pump is running continuously and that there is a steady stream of water from the circulation return in the spa.
When to call a technician: If HFL persists after these steps, the circulation pump may be failing or there may be an internal plumbing restriction that requires professional service.

Display shows HFL; spa may shut down heater but pumps still run.

Possible Causes