High Loop


Some expensive dishwashers have the high loop built in. I always mention that in the report so that they have to research it.

Even the expensive ones (Bosch and Asko anyway) that have a built-in air gap still require and external air gap----countertop or Johnson-T.

I believe the high loop or air gap are required so if something gets clogged the homeowner will see the water in the bottom of the sink and investigate.

The “built-in” high loops are typically on the supply side of the dish washing machines, not the drain/waste side.

The method in your picture Brian, is an improper installation - period. Any connection that allows the potential for waste from the disposal to enter the drain line is improper (the drainline must slope downhill to the disposal connection) even if there is a high loop or air-gap device.

If your jurisdiction follows the UPC, an above-the-flood-rim air gap device is required, regardless of the built in features.

Hence the picture of the defect Jeff.:slight_smile:

If the dishwasher drain piping looped higher than the bottom of the sink I would not have called it out (1980’s condo). Although with an 03 remodel an air gap probably should have been installed.

When I explain it to clients I tell them if the disposal backs up, without loop or air gap, you may not be aware of it as the waste will drain into the dishwasher. With a loop or air gap you will become aware as the sink will backup.

I have found that the ones with “built in” air gaps have the drain line routed through the top of the (cabinet) instead of being routed through the bottom, easy to figure why.:wink:

Check #'s and call to be sure.

Jeff, where did you find this info?

I remember looking through the manual on a new unit and finding something about the internal drain having a high loop. I can’t remember the brand.

I think most units have a solenoid valve or check valve to prevent backflow into the supply line. No high loop needed for that.

Above the flood rim is different from “higher than the bottom of the sink.”

If the top of the loop is not higher than the flood rim, i.e., somewhere between the bottom of the sink and the top of the flood rim, then there still is the possibility of contaminated water backflowing into the dishwasher.

I’ll have to research that.

A built-in high loop on the drain/waste side would require removal of the dishwasher to clear a blockage. There are some “higher end” models with built in disposals that drain debris quite effectively, however, in our state, they still require an air-gap.

Blockages would not occur in the drain line itself unless someone has removed the strainer or screen in the bottom of the dishwasher.

It would be possible for debris to come from the sink direction I guess but dishwashers have a pump to force the water out.