First unit I ever heard of that has a tank solely for the washing machine. I'd bet a large coke someone gave you bad info.
It's easy to figure out.......a bit time consuming.......just run one water spigot at a time, and see where it dumps into.
"Next to prayer, fishing is the most personal relationship of man" Herbert Hoover
"American by Birth, Southern by the Grace of God"Lewis Grizzard
2016 GMC Denali 3500Dually--2017 CC 36CKTS