Display shows E05 and no water flows through the softener; household has no water when unit is not in bypass.

Safety first: Immediately place the softener in bypass to restore temporary water service. Then unplug the unit and close the inlet valve before disassembly.

• Check for external shutoff: Confirm that the inlet and outlet isolation valves are fully open and that the bypass is not partially engaged.
• Inspect valve internals: Remove the control valve cover and access the piston assembly per Crystal Quest service instructions. Look for broken pieces of plastic, resin beads, or debris obstructing the service port.
• Rebuild piston/seals: If the piston is scored, swollen, or jammed, replace it along with the seal and spacer stack using a Crystal Quest piston and seal kit. Lubricate O‑rings with silicone grease only.
• Verify cam alignment: Ensure the drive cam is correctly indexed to the piston and that the valve is set to the SERVICE position before reattaching the motor.
• Test flow: Restore water slowly with the unit in service. Check for normal flow and absence of E05. If blockage recurs, inspect the upstream plumbing for debris or a failed prefilter sending media into the valve.