La Marzocco Overactive Expansion Valve / Overpressure Bypass

Water backs up into drip tray during brewing; significant flow from drain hose while pulling a shot.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Expansion valve set too low, debris preventing proper sealing, worn expansion valve spring, excessive pump pressure

Safety first: Turn OFF and unplug the machine before adjusting valves.

Steps:

Measure brew pressure: Use a portafilter gauge to confirm pump pressure.
Adjust pump first: Set pump pressure to spec (~9 bar). Excessive pressure will cause the expansion valve to open.
Inspect expansion valve: Remove and clean the valve, checking for debris on the seat and spring.
Adjust expansion valve: If adjustable, set it to open slightly above brew pressure (per La Marzocco spec). Replace if it cannot be adjusted or is worn.

Medium 3/5

Expansion Valve

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