Standard extraction

Open

Extraction with pre-infusion

Open

Extraction with low pressure / soft pre-infusion

Purge

Leaking solenoid valve

Extractions on a grouphead with a leaking solenoid valve often include long tails of low flow rate after the disengage.

Leaking solenoid valves may also produce flow events which are a continuous stream at low flow rate when no extractions are running.