Plumbing leak help

Looks like a shut off valve, but a check valve makes more sense.

That is a vacuum breaker/check valve for the black tank flusher, the manufacturer states that they can expel water and are to be installed where that water will do no damage. RV manufacturer’s cannot read and put them wherever it is convenient for them. Some folks replace with a higher quality one, but I just simply eliminated the stupid thing and made sure there is a check valve in the inlet. We can expect others to point out the error of my ways.