Check valve (general)

ISO 10628-2 (group 22, check valves) / PIP PIC001

Drawn as

Bow-tie with the downstream (outlet) triangle filled black, and a flow arrow above it.

Meaning

Non-return valve: flow only in the arrow direction. Found on pump discharges, compressor discharges and anywhere back-flow must be stopped. The filled side points the way flow goes. Swing type is the default when the legend does not say.

Variants

ISA/US style: an open triangle against a vertical bar (the seat), with or without an arrow
Some legends draw "N" or "NRV" beside a plain bow-tie
Check the arrow, not the fill, for direction if the drawing is mirrored