If you pull the plug on the back side of the "T", you can get a 1/2" MPT X 1/4" hose barb, a short piece of polybraid hose, and a couple of clamps, and you've got it licked.
Stainless is way good for inlet plumbing. SS, brass, or plastic.
The easy start consists of a ball and seat with a spring. At zero pressure, the ball unseats from its mating surface, allowing the water to bypass...like an unloader. When the machine comes up to speed and pressure, the ball seats, and the machine works as normal.