How is a dishwasher supposed to be vented according to the general plumbing code

Hi Jackkann...

A dishwasher is not usually vented separately. It usually connects into the drain from a kitchen sink and the drain from the kitchen sink is vented.

If you install an individual ptrap for a dishwasher then that would need to be vented or connected to a vent just like any other fixture with a trap.

Hope that helps...

MARK

How is a dishwasher supposed to be vented according to the general plumbing code

Marks answer's bang on. If a DW is connected to a kitchen sink through a disposal nor a branch tailpiece then it's vented and trapped by the sink.
Anything else requires both a trap and a vent. Regards, Tom