Thread: Dishwasher drain line connection

Looks like the plumber got a little creative. With multiple dishwashers how should the drain lines be connected. Pay no attention to the radiant heat manifold, exposed romex, and loose plumbing lines under the sink

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Very cute

Should have used a tail piece with a disposal tee.

Originally Posted by Michael Larson

Should have used a tail piece with a disposal tee.

He did... his is horizontal.

Originally Posted by mathew stouffer

With multiple dishwashers how should the drain lines be connected.

Into tailpieces with the tap for dishwashers, but the tailpiece should be ... vertical.

Should have installed a tailpiece with a tap under the left sink and connected one dishwasher to that, then the other dishwasher as he did, only with the disposal connected to the 90 degree elbow down to its own trap and back to a wye cleanout where both traps would be connected into the drain to the vent.

Of course, the above will now lead into the often discussed "single traps on a trap arm" discussion we have had so many times here.

(underlining and bold are mine)
- P3201.6 Number of fixtures per trap. Each plumbing fixture shall be separately trapped by a water seal trap. The vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches (610 mm) and the horizontal distance shall not exceed 30 inches (762 mm) measured from the center line of the fixture outlet to the centerline of the inlet of the trap. The height of a clothes washer standpipe above a trap shall conform to Section P2706.2. Fixtures shall not be double trapped.
- - Exceptions:
- - - 1. Fixtures that have integral traps.

- - - 2. A single trap shall be permitted to serve two or three like fixtures limited to kitchen sinks, laundry tubs and lavatories. Such fixtures shall be adjacent to each other and located in the same room with a continuous waste arrangement. The trap shall be installed at the center fixture where three fixtures are installed. Common trapped fixture outlets shall be not more than 30 inches (762 mm) apart. (Jerry's note: "shall be PERMITTED" DOES NOT mean "is REQUIRED", thus that sink is ALSO "PERMITTED" to have two traps, one for each compartment.)
- - - 3. Connection of a laundry tray waste line into a standpipe for the automatic clothes-washer drain is permitted in accordance with Section P2706.2.1.

Also refer to Table P3201.7: (bold is mine)
- TABLE P3201.7
- - SIZE OF TRAPS AND TRAP ARMS FOR PLUMBING FIXTURES
- - - Kitchen sink (one or two traps, with or without dishwasher and garbage grinder)