Ok, this is weird. The kitchen sink is against the exterior wall, and the dishwasher is located inside of an island right above where you see the dishwasher drain. A regular high loop drain would be connected to the kitchen sink plumbing whenever the dishwasher is next to the sink. However, this installation does not have a High loop drain and the drain goes straight through the floor and ties into the kitchen sink drain. Although I am not a fan of the installation, it is trapped and I don’t see any possibility of backflow problems. Any Licensed Plumbers in here? What are your thoughts?
Until a “licensed” plumber shows up here is something to ponder: every p-trap should be vented. Don’t forget an air-gap or high-loop, depending on your local codes.
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I see a high loop backflow preventer on the dishwasher drain line above a water trap.
Missing trap cleanout.
Is that poly-B potable domestic supply tubing?
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Why not consult a local plumber?
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That was done by a “local” plumber 
I doubt that. Even the worst plumbers should have a better primer and glue joint.
He was just making sure he primed it real good!
Yup even got the outside of the fittings for good measure.
I fixed it for you, Simon. 
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Looks ok to me…