We redid our kitchen about six months ago and installed a Bosch 800 series dishwasher as part of the remodel. I've been really pleased with it; it's dead silent and cleans well, which is all I expect from a dishwasher. Then a month ago I got some error codes- E15 Aquastop Watertap. Bosch customer service was going to take a month to get here, so I called an appliance repair firm that had helped us in the past.

The guy came and spent 45 minutes unclogging the drain - said it was filled with gunk. I was surprised by this because I'm pretty neurotic (unnecessarily I know) about precleaning food before the loading the dishwasher - we only use it every other night and I don't like the yuck factor of anything that could stink. I had done some reading here and elsewhere on the internet and thought perhaps I was having the same mysterious gunk problem due to detergent that has been discussed here.

Then today, I got the same error code - it actually came on while I was using the sink and garbage disposal. Hadn't touched the dishwasher in 2 days due to travel. And so, thinking it was kind of weird for the dishwasher drain to suddenly clog when not in use and upset that I was going to have to call the repair guy again, spend another $180 and stay home from work, I did some more internet sleuthing.

I saw one suggestion that installation and hose placement could be the cause of water backup, and then started poking around the Bosch installation manual. I have no air gap, and the hose is not looped at all - it runs from the dishwasher across the sink cabinet to the garbage disposal and is primarily at a pitch below the entry point from the dishwasher. (I tried to take a photo, posted below.)

I think this means it was installed incorrectly, and that water may be washing back from the sink but as someone with ZERO plumbing skills, I wanted to come here first before I get angry (again) with the contractor who did our kitchen renovation. Either way, I'm probably going to have to start with a repair person, but can anyone here tell me if I might be onto something? And should a contractor know that a high loop is required for a dishwasher installation - a quick internet search makes it seem like this is the norm, but obviously, again, I'm clueless so I didn't know if this might be some super specialized only-in-new-Bosch models kind of thing that a run-of-the-mill contractor might not be aware of....

Thanks for any help!

Newcastleton, Scottish Borders, UK Dishwasher Installation Professionals