I had been resisting using plastic pipe, and these fittings with rubber o-rings. But right then, faced with limited time, I decided to give them a try. Bradley ford SharkBite Push-to Connect ...

National Pipe Tapered Fuel (NPTF ... and never loosened. -Straight-Thread O-Ring Fittings are the ones you thread into place, then tighten a nut on the fitting against an 0-ring built into ...

Flat-face hydraulic fittings and connectors have an oil ring in a groove in the face of the male fitting. That O-ring seals against the flat, machined face in the corresponding female fitting.