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OPV (over-pressure valve)
Spring-loaded valve that caps brew pressure at a set point (typically 9–10 bar) by venting excess pump output back to the reservoir.
Category: Espresso Machine — Groups & Brew Path
A spring-loaded valve in the brew water line that opens when pressure exceeds a set limit (typically 9–11 bar), bleeding excess pressure back to the reservoir or drain. Prevents over-pressurisation of the puck.
Why it matters — The OPV is what limits the actual pressure reaching the puck. Most prosumer machines ship with the OPV set at 10–11 bar; dialling down to 9 bar improves the majority of shots by reducing channelling.
Good to know
- Adjusting the OPV requires a blind basket fitted with a pressure gauge. Most home users can do it in 30 minutes with the right kit.
- Half a turn of the OPV adjustment screw typically changes pressure by 0.5–1 bar — adjust in small steps.
Related: OPV Parts