I have a power washer unloader (General Pump ZK1) that has an "3/8 BSPP-M" outlet. I understand that BSPP is a parallel thread that requires a washer to seal, but this fitting doesn't have a flat face for a washer to press against; rather, it has a concave flare that would seem to be the sealing surface.
So what's this called? Is there such a thing as a BSPP-M fitting that seals with a flare instead of a washer? I just can't seem to find the right term to describe this. I'm ultimately trying to connect a 3/8 NPT-M hose to it...