you'll be fine with current 1/2" , and your installer doesn't know this, because he got trained by Miele and they brainwashed him.

How was the dishwasher hose going to be configured by your Miele expert? With a high loop? A loop up to the countertop and a drop down to the sink drain?

it is OK to have the slightly larger drain hose connect onto a slightly smaller opening; the drain water drops by gravity and gets into the sink drain, nonetheless, notwithstanding, in any case, etc. Water drops through; it is not pumped through. It gets pumped up to the top of the hose which is positioned in a "Loop" configuration so that there is a local high point in the middle of the hose and then the hose drops down to the drain. This makes water fall in a free-fall drop to the drain; it's not pumped right up to the sink drain's Dishwasher Tee.

Your socalled Miele installer doesn't know much: he has received the training and now he is the expert they gave you and whom you must rely on. But, his background is not rich and deep. Miele employees in general are well trained but overtrained in isolation so they do not have a broad view of reality. This is a subtle way to say they have drunk very much of the elixir of thought control, like Jonestown KoolAid.

If you ask around, you might misstate the "drain" case, so I'll give you a few more tidbits that might help to explain things.

(1.)/. In DWV plumbing, one may not reduce the drainpipe size, but this only applies After The P Trap, and for a good reason, which does not apply Prior To The P trap which is where your hose is. So, many would-be helpers will mix themselves up if you talk about reducing a drain size. HOW you explain your hose connection diameter to someone else is the key to getting them to help you. An average handyman won't be able to help explain why things are the way they are with the 1/2" diameter.

(2.)/. There are many other dishwashers with a wider diameter hose, so you could call another manufacturer (e.g. Asko) and ask if it hurts in any way to connect to a 1/2" diameter opening. The air opening of the 1/2" diameter Tee (or Wye) allows Every Other Dishwasher's reject water to cross that opening and reach the sink drain, and all dishwashers spew out roughly the same amount of water at the end of a cycle.

Hope this helps explain what is what and why a Miele trained expert cannot figure it out. Miele people are all good people, but they are over trained in certain ways.

"Water drops through; it is not pumped through. "

Sorry daviro1 - THIS IS TOTALLY INCORRECT !!!

Maybe you should get A CLUE before you start dispensing advice about matters that affect other people's wallets.

Mieles do PUMP out the drain water! What do you thing the impeller/pump that is in the sump is doing during a drain cycle??? Sheeze, you are partially correct though. With a high loop the water will drain by gravity from the high point - AFTER THE PUMP HAS TURNED OFF! The hose will be under pressure as long as the pump is on so it is forcing the water through whatever size hole you have the hose hooked up to.

Besides, a high loop is a a great idea with a Miele but they will function without one! In fact you can even drain them straight down into a cellar or basement drain.

Sure IT CAN BE hooked up to a 1/2" opening , but why would one take the chance of setting off the drain sensor in their $1500+ DW or risk the less than stellar connection btw. the 7/8" hose and the 1/2" drain connection ??? Just get the correct tailpiece. I'm sure you have them in Canada, tell your plumber to quit being lazy.

BTW david - many "Miele Trained" installers don't work for Miele, and some have not even sat through the classes ! Many times their bosses sit and hopefully impart the training onto their minions. Anyway , part of the Miele's training is to impart practices that work with THEIR MACHINES so that they work properly and do not cause premature failure or generate service calls. The practices are by no means the only way to to do things, but they work for their products, why not just follow the instructions ??? It's not as if they are asking you to use a hookup that is not widely available or has to be special ordered or costs $106.

It really boils down to laziness - just get the correct parts and quit trying to Rube Goldberg the install to fit the materials you have on your truck! Our jobs are spec'd with a separate p-trap for the DW drain and the diagrams and pictures are sent to the plumbers beforehand, and still some showup with those branch pipes or knock out the disposer hole. They then try to sell me on how "you'll be fine with " it this way, only to get beet red when I show them the spec, and the correspondence showing it how we want it. They are not happy when they have to by a new disposal, especially the ones we use, because they we lazy or just knew better than the person ordering the service.

Re: ASKO - they do the same as Miele in that they guide the install to fit the engineering on their machine. It is not the SAME ENGINEERING, so Asko has a different intake line and discharge line which has a high loop built into it already as well as a step down fitting attached to mate to several sized drain tubes. That's what works for their units.

How bout you call them up davidro1 and ask them about ditching the high loop and running the hose straight out the bottom of the unit into the basement laundry and come back and report to us what they say about that !

unix... bottom line is that it's not a good idea to hook up your DW to a 1/2" drain. It can be done, and it can work, but that's not the same thing.

I went to more than a few plumbing places to look for the part with the 7/8" sized branch connection. They all gave me a funny look and said we only sell the 1/2" version.

Weird. Google says there are lots of places in the USA that sell it. Unfortunately, I live in Canada.
RWW

I was rummaging around HD today thinking about this. I saw the plastic 1.5" tail piece and I thought the 0.5" branch was way too small. I'd look for something bigger from a plumbing supply house.

Here is a link that might be useful: tail piece

I couldn't find it at the big box stores but a quick trip to a "real" plumbing supply quickly solved my problem.

(LOL antss!)

hey antss i enjoyed you rantss,
very good style.
t he pump the drain and the water falling down the hose.
a nursery rhyme for the trade.