Dishwasher High Drain Loops / Air-Gaps

Dishwashers, if present, are a permanent fixture that will get inspected and tested in a standard Texas home inspection. What I’ve found to be the  most prevalent defciency with dishwashers doesn’t actually have anything to do with the dishwasher itself, but it’s drain hose.

All of the dishwasher manufacturer’s require some method of air-gap or back-flow prevention to be used to prevent dirty dishwater from washing back into the dishwasher barrel. Back-flow prevention isn’t quite the exact term but this concept of an air-gap is quite prevalent in plumbing and the idea is to stop or limit the potential syphoning of water to places it shouldn’t go. Imagine if water was to buildup in your food waste disposer and then flow backwards into your clean dishes sitting in the dishwasher. That would be gross!

There are a couple ways to create this air-gap. One of them is to install a fitting near the top of the sink / countertop, appropriately named an “air-gap”. The dishwasher drain hose connects to the air-gap and another hose leads from the air-gap to the drain / garbage disposal, and the air-gap creates a break in the line. This fitting occupies the space that you would normally use for something like a soap dispenser and is generally unsightly, so it’s pretty rare to see these things anymore.

no dishwasher drain loopno dishwasher drain loop

The much more practical and easy-to-install method is a dishwasher drain loop.


How to Install a Dishwasher High Drain Loop

Simply taking the dishwasher drain hose and elevating at least one section of the hose above the garbage disposal inlet or drain inlet into the sink drain will prevent dirty water from “back-flowing” into your dishwasher barrel. There are many ways to acheve this loop. One of the easiest I’ve found is to screw a drywall screw gently into the cabinetry near the countertop (not going more than a quarter-inch deep or so), and tying a wire-tie or a zip-tie to both the screw and the drain hose.

The correct way to install a dishwasher high drain loopdishwasher drain loop bent hosealternative bend for dishwasher drain loop

Another very common means of installing a dishwasher high loop that I see, particularly on new-build homes, is installing the dishwasher drain through a hole drilled higher in the adjacent cabinet panel. This way, the drain hose will have to fit through the hole at the high point in the cabinet and this will give you a drain loop without requiring any screws or ties. On the flip side, this is only practical on new homes or if you are pulling the dishwasher out to replace it.

alternative dishwasher high-loopalternative dishwasher high-loop

Viola! You’ve just elevated the drain hose above the discharge point at the garbage disposal. Theoretically, dirty water can no longer flow back into the dishwasher (as water doesn’t run uphill) and you can check this off of your list of items to compete from the home inspection report.


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