E18 displayed and the unit reports a resin tank overpressure or safety shutoff condition.

Safety first: Immediately close the inlet valve and unplug the unit if E18 appears. Do not attempt to operate the softener under suspected overpressure.

• Check downstream valves: Ensure all shutoff valves after the softener are open and that there is a path for water to flow.
• Inspect outlet plumbing: Look for kinks or obstructions in the outlet line. If a check valve or backflow preventer is installed, verify it is functioning correctly.
• Examine pressure relief: Locate the AquaSoft pressure relief valve on the control head. Ensure the discharge line is not blocked and that the valve is not leaking or stuck.
• Check for resin blockage: If flow is restricted, the lower distributor or riser tube may be clogged with resin fines. This typically requires depressurizing the system, removing the control head, and inspecting the riser and bottom distributor.
• Contact a professional: Overpressure conditions can be hazardous. If you are unsure, have a qualified technician inspect the system.