I was looking at a rinser that only had one way to to fill it up and one way to drain. it used the same pipe. Now mind you there was (I believe a backup valve?) 2 solonoids that when one is open that let the water in the one going to the drain is closed, and when the drain is open the supply is closed.

The only problem I have is that for a short section about 2ft to 3ft the drain water can be mixed with the supply water, (thats just the residual). I admit im not a plumber, but would this set up be legal?? Even if it was I would not want anything I got with this set up. Any guidance would be appreciated.