I love watching the athletes do their performances on the trapeze, but this sink guy was no trap-ease artist.
Water can't be expected to flow up. It will with pressure from one end when forced. But not in a drain situation. Drainage will only go down to the level the weight of the water will settle to and stay.
But not up from there!
According to the feature list this is a "New Dishwasher, Disposal and Kitchen Sink!" (happy dance)
This drain arrangement expects the water to flow up from the lower red dot to the upper red dot!
That blue line represents the level at which the water settles and stays.
So, there is always water in the disposal.
When you look into the sink drain you can see the water sitting in the disposal.
The amount of water sitting in that drain now is the same amount that always stays.
When water is running into the disposal only as much as goes in will go out.
My client asked, "What does that mean?"
It means water will back up into the sink on the other side.
To answer I said, "Watch what happens when I force the dishwasher to discharge its water. See how the dishwasher drain tube goes right into the disposal?"
So, pushing the 'Cancel' button on the dishwasher, we just watched.
As the dishwasher let go of its full load, the sink on the left side filled up with some very interesting stuff.
"Imagine what this will look like when you are living in the house and food stuff is going down the disposal and coming out of the dishwasher. And, imagine what kind of yum-yum is always sitting in your disposal and drain waiting for the next time you turn the water on or run the dishwasher. What do you think that will begin to smell like soon?"
Her response was what I expected, "Oh, yuck!"
Then, thinking further, "Will I smell sewer gas?"
So, we sat down together in front of the sink and with flashlight and finger I explained how this had to be completely reconfigured so that the disposal discharges into the drain higher than the convenient second trap.
"Properly done you won't smell sewer gases."
That red dot is the same place as the high red dot on the first photo. So a proper trap arrangement is possible.
She felt better knowing that. "What does the drain need now?"
"A professional plumber..." Always a Best Practice.
My recommendation: traps want water to easily flow, and downward. Hopefully what remains is clean water! Sometimes I can look under a sink and predict what will happen. That's always a great object lesson for my clients. It can get yucky, to be sure, but it's a really fun class!
Jay Markanich Real Estate Inspections, LLC 
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560
Interesting stuff is an understatement for sure. Nasty I bet
This was one mess James. Easily fixed though.
Yes, this is some of the stupid stuff that happens when you don't hire a licensed plumber. Dumb.
The good friend, relative or homeowner here Debbie! Not good.
Good morning Jay,
I agree call the plumber as it looks like a maze to me; even with the explanation.
Make yourself a great day.
Hi Jay,
Looks like some of the plumbing I had been finding here last month.
Always hire a professional.
Have a nice day in Bristow.
Best, Clint McKie
Jay, looks like a plate under the drain. Nice touch!
Guessing that made the top of the "to do" list on this buyer's amendment !
There is a lot going on there Jay! Plumbing is more than just getting everything connected. The answer is not as complicated as this; it can be done.
Yucky is such a fun word, Jay. Since a proper trap arrangement is possible, it's hard to fathom why it wasn't done right in the 1st place...
Thanks for sharing,
Bruce
Plumbing is NOT the place to cut corners.
Jay, that is amazing that whoever did that drain would think it could work!
Jay, but the pieces all fit together---it must be correct!
Most excellent post and the trainee that installed the trap needs to keep his trap shut
This is what happens when "uncle louie" does plumbing. I can't imagine that a licensed plumer did that.
Good catch as always. Good thing it wasn't a vacant home. You would have needed a gas mask.
Good explanation for the laymen out here. Really makes you wonder what installers are thinking. I guess they aren't.
Gravity is such a cruel weapon that often works against the do it yourselfer!
Jay it seem amazing what you find in homes today, it always a challege to not smile in front of the customer when doing your job I am sure.
Hi Jay, I am surprised someone actually installed a drain like that. If I find out who did it I may run the other way. Thanks for the post.
It's simply amazing how many of these types of incorrect plumbing issues are found during home inspections. Is garbage dispsoal/dishwasher installation even taught any more?
Great post as usual.
Jay- to that, I can only say "ICK!"
Must have been the same plumber that initially installed my dishwasher.
Every time they would come home after a few days away, the sewer smell in the kitchen would be awful. A home mechanic job for sure
oops! that has been on the Honey Do list for ages... dont worry Charlie 10 thumbs will get right on it.
Jay - unless that was a home made job the person that did it should not be working. Sometimes handymen do things like this. It does not pay.
There is always a story but I think this one is a potential nightmare plus the disposal will probably retire early.
Anybody can install a dishwasher. I'll just a demonstration at Home Depot, and if i forget, I'll just google " Dishwasher Installations for Dummys". Being able to see the water back up sure got the point across!
Jay, gravity's something we have to deal with everyday. What was that person thinking?
Bruce - I have to think this guy thinks it is proper!
Corners Alan? I don't see no stinkin' corners.
It did work Joan, until I showed up. Somehow now it does not any longer.
It is a puzzle well done Charlie. Now, where is that hip bone attached?
Richie - in this case, he should stay far away!
I doubt one did Geoff. Certainly the well-meaning friend or homeowner.
It was fun Scott. Sitting on the floor showing my client where things need changing was a bit fun too.
No think Than. This show no think.
Gravity works pretty well Gary. A very consistent phenomenon. You'd think people would understand it after a couple of years...
I had fun with this one Chuck. It became a great plumbing lesson!
S&L - this is a serious installation! Seriously deficienct, but serious!
Denny - don't know if it is taught, but it seems to me there are classes on everything at the home stores!
That would work Kathy. Succint!
Catherine - it's nice of you to share!
Ed - I think the smell would get substantially worse over time.
Never heard of that guy Robert, but he sounds like a problem getting all around!
Grant - if this guy is paid for work like this he will starve not long from now.
Bill - a nightmare for sure, or a short, scary story!
Jeff - I had fun showing that one to my client. She was amazed that I could predict it. Aw shucks.
You aren't asking me are you Tom? I don't know, for sure! It sure made for a great post!
Jay -- this is most interesting. I always learn something new when I read your posts.
Blah, blah, blah. Don't eat on those dishes. I hope a plumber didn't do that.
Good morning, Jay. The folks need to learn how to train their water. As we all know, trained water will flow uphill.
Joan - basic rule of plumbing -- make sure water flows downhill. Nuff said!
Mike - maybe he was an electrician?
Michael - trained along with the flea circus. Maybe that's what the plate down there is for.