Gees are you sure it is just a dishwasher?
Maybe you are saying difficult to get a loop seal to protect from any drainage back into the dishwasher.
Sounds like the situation where you buy a new rubber drain hose of the proper length to allow it to be routed in a proper manner. Your hook up point might be different than the last guy, same hose isn't exactly long enough for the job.
Forget all the splicing and jury rigging. Get a hose long enough for the job. You are unclear exactly how / what the hook up point is into the drain system. Just have to fit that up as required. Normally that point is above the trap of the sink, either into the normal supplied port on a garbage disposal or to a fitting on the drain line. The drain hose is looped up high enough over that point so normal drain water from the sink can't flow back into the dishwasher.
Some local rules and regs require what is known as an air gap device be installed if the dishwasher is draining into an under sink type drain line. Some dishwashers have it built into their drain systems. Basically it is a device that installs thru the sink, it provides a drain height point above the highest level in the sink. Just web search for "dishwasher drains air gap". Used to prevent siphon flows from the dishwasher when the pump is not running.
Don't try to put air brakes on the dishwasher, definitely not required.