Steam trap

ISO 10628-2 (groups 24-25, fittings and piping) / PIP PIC001

Drawn as

A small circle on the line with "T" inside.

Meaning

Lets condensate out of a steam line or tracer while holding steam back. Seen at the end of steam tracers and on steam-line drip legs. Becomes steam-trap.

Variants

ISO-style legends draw a square on its corner with a filled dot
Some write "ST" next to a small square