I had to replace one of the low point drain valves that sit in the water connection center on our year and model. I got the valve from Camping World's RV Parts store (this CW had an RV dealership). This valve goes on the pex line.
I have also added a drain valve (for better control) and hose connection (to route water away from the rig) on the pex line on the drain of our fresh water tank. I got those fittings at either Lowe's or Home Depot.
I also added a drain valve and hose connection at the exterior end of the cold water low point drain. It provides an easy access hookup for my wash hose for those times the park's connection is a long ways away. I just connect to that point and turn on the low point drain while attached to the park's city water. I suppose I also could maybe convince some parks I'm using my own water to wash my rig....