Lay-Z-Spa displays E04 and stops all functions; unit may not respond to button presses.

Safety first: Disconnect the spa from mains power before adjusting water level or removing the pump unit.

• 1. Check water level: Ensure the spa is filled between the MIN and MAX lines. If the heater was run with low water, allow the unit to cool for at least 30 minutes before restarting.
• 2. Remove airlocks: With the pump attached and water level correct, briefly loosen the filter housing cap to release trapped air, then retighten. Run the filter function and confirm steady water flow from the outlet.
• 3. Power reset: Unplug the spa for 10–15 minutes, then plug back in and reset the RCD. Try running only the filter first, then enable the heater.
• 4. Inspect for leaks around heater: Check the underside of the pump/heater unit and hose connections for signs of water leaks that could affect sensors.
• If E04 continues: The dry-run/thermal cut-out sensor or internal thermal fuse may be permanently open. These are safety-critical parts and not user-serviceable on most Lay‑Z‑Spa models. Contact Lay‑Z‑Spa support; the heater assembly or entire pump unit may need replacement.