Solenoid valves control the flow of water throughout the espresso machine hydraulic system. The valves are electronic. With regards the water hydraulics they have two main functions.
- Controlled by the electronic level control they open and close to fill the boiler on a HX and a steam boiler on a La Marzocco.
- Under manual control by the user or by automatic control from the volumetric dosing system the valve opens to allow water from the HX to the coffee grounds (in a HX machine) and allow water to pass from brew boiler to coffee grounds in a La Marzocco.
Solenoids are either 2-way or 3-way:
- 2 way valves function in just two ways- inlet and outlet. Water is supplied under pressure to the inlet side of the valve. When the coil is activated, the pressurized water or steam is allowed to pass, and exits the outlet side of the valve.
- 3 way valves function nearly the same way, they also include a discharge to relieve any pressure in the system when the valve is deactivated. These are most commonly used in group heads, and this discharge is where the backflush soap exits.
Some common problems with solenoids are:
- Noise - Buzzing or Chattering
- Leaks - An overfilled boiler, dripping water or steam escaping
- Not Opening - If your valve does not click, it is not opening