My new Samsung dishwasher emits a sewage odor (started with the 1st use) through the dishwasher air vent, but only while it's running. I think its pulling air through the drain hose while its running. It actually smells up all the surrounding cabinets too. The installer felt that running the drain hose up and over the cabinet wall to connect with garbage disposal would create a sufficient air trap. Shouldn't the drain hose have an actual 'loop' before connecting to the garbage disposal? I did not notice this odor with the old dishwasher. Thanks for any advice.
You need a loop (it should go above where the dishwasher enters the disposal) or an airgap to prevent the backflow of drainage water into the dishwasher. The smell could be coming from the inside of your garbage disposal.
The line should definitely be arranged like this photo, where a portion of the line curves above where it enters your disposal.