Anyone know the reason for this odd design for dishwasher water inlet?

Who knows, but IMO when you get to that stage of disassebly with an

I suspect it's intended as an anti-siphon device.

It involved removing two screws.

And there's the self-education of seeing how it works.

Or not learning. I'll bet uncountably many dollars have been spent in the last year or two replacing dishwashers that no longer clean when the real cause of dirty dishes was the absence of phosphates in the detergent.

I can imagine the angst of the average housewife when, after spending $1,200.00 on a new machine, finds that the new machine STILL doesn't clean as well as the one hauled off as heavy trash a month or so ago!

Of course, throwing away an 80's vintage dishwasher might not be a bad idea, even after you spend the time educating yourself on how it works and why it's broken.

Take the learning experience and file it away, then go buy a much more efficient and certainly quieter unit.

Quieter I can grip.

But how is a modern dishwasher that much more "efficient" than a 1980's model?

I did an even more extensive level of disassembly of an old KAid D/W (79)... got it all back to together and it ran for two weeks. :( Both a used on on craigslist for $50.... still running 5 years later.

Totally true... typically, the fixes are simple. The learning process is worth the time.

Often an eval & fix can take less time than buying a new one.. It all depends.

Define "efficient". If you mean better at cleaning, sure, there are dishwashers that are more "efficient" than others. Later ones are more "efficient" than older ones, too, since the phosphates have been cut back.