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