The drain for a washer is basically connected right to the bottom of the tank. If you dip the end of the hose lower than the water level in the tank, it will gravity drain. The hose must rise up higher than the level of water in the tank.
Now, I know Hawaii is "different" but in most places running gray wash water into the garden is illegal. A true gray water system is much more complicated . The water must be filtered and cannot be applied on the surface.
I used to live in Eva Beach; even out there I don't remember that water was such a problem that we needed to worry about saving the wash water.