This is behind my dish washer and the drain hose has been like that for awhile (by laying flat on the ground):
I believe it should be hang up to make a loop on top, right? But there is no where to hang it behind the dish washer.
Under the sink, it is a long hose. I am wondering if I should mount it on the wall of the sink cabinet?
Please advise.
I think you have the right idea. It can't go behind the dishwasher - there is normally no space at all between the dishwasher and the wall.
Typically a dishwasher will be mounted next to a sink. The hose should be long enough that you can loop it up on the side or behind the sink so that it goes up to the bottom of the counter, or at least a few inches higher than the sink drain.
If the hose won't stay up by itself, screw a piece of metal or plastic strapping to the side or back of the sink cabinet near the top and loop it loosely around the hose to hold it up. Just don't loop it so tight that it crimps the hose.
Quite odd to see the dishwasher drain line heading directly to a wall drain connection, IMO (if that is indeed what the picture shows). Normally that would connect to an auxiliary drain port on the side of the garbage disposer or a wye connector in the sink drain pipe, after routing through an air gap device attached to the sink or countertop.
It sure looks like there is a "loop" device in the upper-middle area of the dishwasher rear panel where you could use a zip-tie to suspend the hose in a looped configuration; many modern dishwashers have the drain hose pre-routed this way on the rear panel...
