Display shows Err4 and brine draw does not occur during regeneration

Safety first: Disconnect power and place the Marlo softener in bypass. Wear gloves and eye protection when working around salt and brine.

Step-by-step checks:

• 1. Check brine tank level: Ensure there is adequate water in the brine tank to cover the air check at the bottom of the brine well. If the tank is completely dry, the unit cannot draw brine.
• 2. Inspect brine line: Follow the brine line from the Marlo control valve to the brine tank. Look for kinks, pinches, or leaks. Tighten compression nuts and replace cracked tubing.
• 3. Clean brine injector: Remove the injector cap on the valve head (usually labeled "Injector" or located under a small cover). Carefully remove the injector nozzle and throat. Soak them in warm water and vinegar to dissolve scale, then rinse thoroughly. Ensure all small orifices are clear.
• 4. Check brine valve and air check: Remove and inspect the brine valve assembly and the air check at the bottom of the brine well. Make sure the ball or flapper moves freely and is not fouled with salt mush or debris.
• 5. Reassemble and test draw: Reinstall all components, restore power, and take the unit out of bypass. Start a manual regeneration and observe the brine line during the brine draw stage. You should see or feel suction at the brine line and a gradual drop in brine tank water level.

When to replace parts: Replace the Marlo brine injector kit if it is damaged or heavily scaled. Replace the brine valve assembly or air check valve if they do not move freely or seal properly.