E04 appears on the display and the pump runs but no coffee is dispensed; water may leak internally.

Safety first: Unplug the machine and allow pressure to dissipate for at least 10 minutes before opening any part of the brew circuit.

User-level cleaning:

• Clean brew head: Remove the portafilter or capsule holder. Unscrew and clean the shower screen or capsule piercing plate with a brush and hot water.
• Descale the machine: Run a full descaling cycle to dissolve internal scale that may be blocking the brew path.
• Check capsule system: For Dualit capsule machines, inspect the piercing needles and capsule chamber for foil, coffee grounds, or plastic fragments. Clean carefully with a soft brush.

Advanced checks:

• Inspect OPV: Access the internal overpressure valve on the pump outlet. Check for scale or debris preventing it from opening. Clean or replace as needed.
• Check hoses: Inspect silicone hoses from pump to boiler and from boiler to group head for kinks, blockages, or collapse.

Note: If E04 persists after thorough cleaning and descaling, the OPV or internal tubing may need replacement. Seek professional service if you are not experienced with pressurized systems.