Kitchen Renovation, Time to Plumb for Dishwasher

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Mosh Pit

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1. Actually, it, or an air gap connection, is REQUIRED.
2. Dishwashers typically do NOT have a valve on the drain so the water would just drain out of the dishwasher as it tried to fill.
3. Connecting the dishwasher directly to the drain can cause poluted water to back flow into the dishwasher when the drain line clogs.
4. The way yours is connected sounds like the correct way, although it might not need the "mess" fo pipes you describe.
 
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Jadnashua

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To pass code in many places, you need an air gap to connect the DW to the drainage system. It should NEVER be directly connected into the sewer. If there ever was a backup, you'd get sewage back into the DW, and you might never know it. Not something you really want for supposedly 'clean' dishes!

Installation into the disposer is a common, legal way to do this. But, if that backed up, you still could get crud back into the DW. So, many places require an air gap. This is typically installed through the counter. It is a physical break, or air gap, so a backup cannot cross over and go back into the DW. THEN, it goes into the disposal.

The DW must go through a TRAPPED fitting, which the sink is. While you could run it into another, dedicated trapped location somewhere, it CANNOT be directly connected and must have an air gap (this is NOT an air vent).
 

Jimbo

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A dishwasher uses a 5/8" ID drain. You can NOT do it the way you describe. Besides vent issues, the biggy is that you must drain it into a trap, or you will have sewer gas odors inside the house.

With all due respect, the sink cabinet IS for plumbing. Trying to shortcut plumbing codes for the sake of a nice neat place to store your windex, will lead to big problems.
 

Gary Swart

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The diagram you attached is exactly correct if there is no disposal. If there is a disposal, then the final connection should be to the disposal. I would point out that, while not the recommended way, in some areas, it is permitted to use a high loop without the air gap. Local code must prevail. The air gap is always permitted and in may areas required. As far as the water connection is concerned, the standard way is to tee off of the hot water line going to the sink. The includes a shut off valve (1/4 turn best) and normally is a steel braided flex line of sufficient length to allow the DW to be pulled out without disconnecting the line. There is plenty of space under the washer for the extra line, and there is little need to crowd the under sink area.
 

Jadnashua

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The supply and shutoff can come from any convenient hot water pipe's location. It is more common coming from underneath the sink...a new homeowner might never think to look in the basement if the thing ever did leak after you sold the house, though, so convention has merits.
 
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