OPV adjustment

Tweaking the spring preload on the over-pressure valve to change the maximum pump pressure. Most prosumer machines ship at 10–11 bar; many users dial down to 9 bar for better extraction.

Why it matters — 9 bar is the design target for most espresso baskets. Pressure above 9 bar doesn't help extraction — it compresses the puck and increases the chance of channelling. Dialling down the OPV improves the majority of home shots.

Good to know

• Requires a blind basket fitted with a pressure gauge (an "OPV gauge kit").
• Adjust in small increments. The screw is sensitive — half a turn can shift pressure by 1 bar.

Related: OPV Gauge Kits