The drain line from the dishwasher is definitely required to have a high loop, however, in this instance the high loop may be in the cabinet directly behind the dishwasher where you cannot see it.

Normally when connecting a dishwasher to a drain system that has a disposal, the dishwasher drain line is connected to the disposal dishwasher inlet port, which is the short pipe stubbed out of the side of the disposal directly above the disposal outlet port. (There is a knockout cap inside that port to prevent water from leaking out when a dishwasher is not connected there. When connecting a dishwasher drain to the disposal inlet port the installer has to take a screwdriver and punch the knockout cap out to open the port before attaching the drain line).

In your case the plumber elected to connect the dishwasher drain line to a tailpiece with a dishwasher inlet port. Normally that type of tailpiece would only be used to connect the dishwasher when there is no disposl, but technically speaking, it is still an approved indirect waste connection so that would pass inspection.

In this instance they used the mfg supplied 1/4 bend on the disposal and connected it into a conventional "Center Waste Kit", which is also technically okay, but the problem is that as the discharge from the disposal goes through the black 1/4 bend, then through the white 1/4bend on the waste kit arm, then on to the baffled tee in the center the velocity of flow from the disposal is slowed and it could lead to more frequent clogs in the baffled tee.

The preferred configuration would be to connect the dishwasher drain line to the disposal inlet port, the remove the black 1/4 bend that comes with the disposal and install a "Disposal type center waste kit". In a disposal type kit one horizontal arm has a straight tube that has a flange which will connect directly to the disposal port, while the other arm has the 1/4" bend to connect to the opposite sink.

The only thing I can see in that photo that would not pass code is the tailpiece extension attached between the P-trap and the Trap adapter at the wall. That is prohibited.

Code only allows one slip joint on the output side of the trap weir.(REF: IRC-3201.1 & UPC-1003.2).

The proper method is to extend the pipe from the wall and put the trap adapter where it will connect directly to the trap.

Your detailed answer is most appreciated.

Hubby tackled the pipes today; this is basically what he said: ..."I elevated the drain hose from the dishwasher above the discharge end where it was attached to the drain."

He also said something about remembering that our plumber hadn't done this behind the cabinet.

It all sounds like *Greek* to me; but it probably makes sense to you (?)

Thanks again for your generosity of time and knowledge. Hopefully our smelly sink problem has been corrected!