Plumbing lines commit fully to their innuendo — there is no subtle way to joke about pipes, and pretending otherwise wastes everyone's time. The trade-specific ones (fittings, pressure, stopcocks) earn respect from anyone who has actually held a wrench.
Deliver with confidence or not at all. A mumbled plumbing pun is just a man saying "pipes" at a stranger.
Plumbing innuendo cannot be half-delivered — the listener sees the joke coming from the word "pipes", so the comedy lives entirely in your commitment to finishing it. Trade events and site banter are the native habitat, but these travel surprisingly well: everyone has had a plumbing emergency, so everyone has context. The emergency call-out itself, however, is a professional visit and not an audience.
Fellow trades with equally committed material: electricians, carpenters and builders.

