What is this thing??
 

I'm not sure what this is in the picture. The clear tube comes from the dishwasher, the chrome part sits above the counter where an 'in-counter' soap dispenser would normally be and the black tube was connected to the insinkerator. It's a KitchenAid dishwasher.

Dishwasher air gap.


Generally used when there is no vent off the sink....

Get rid of it. It’s a vacuum breaker keeps water from backing up from a clogged sing into the dish washer, mount on the counter top not under the sink, just loop the washer drain hose high close as possible to the rim line. toss it unless required by your local code.

As ktkelly posted, it's a dishwasher airgap.

It's a very important item in a dishwasher's drain line to prevent contaminated waste water from the sink's drain or garbage disposal from back siphoning back into your dishwasher. Some areas require it by code, while other areas just require running the dishwasher's drain line to a high point under the kitchen cabinet. It's a easier to do the latter but that's a really bad idea in my opinion.

First, let's get this out of the way. Dishwashers come with a backflow preventer valve but like anything else, the valve can fail over time. If it gets stuck in the open position, waste water can drain back into the dishwasher. The following assumes the backflow preventer valve (if there is one) is stuck in the open position.

DRAIN LINE JUST RUN TO HIGH POINT WITHOUT AN AIRGAP:
If the drain line is just run to a high point under the kitchen counter without an airgap, it's true that draining waste water from the kitchen sink into a properly working drain will not travel up hill and drain back into the dishwasher. It's also true that waste water from the dishwasher will flow into the drain and no waste water from the sink will drain back into the dishwasher.

But what happens if the sink's drain gets clogged? Waste water will rise in the sink and if it gets higher than the high point in the dishwasher's drain line, contaminated waste water from the sink drain or garbage disposal will drain back into the dishwasher. The homeowner will probably not even realize that this happened while he/she goes into emergency mode to stop any overflow and fix the clogged drain.

But what if the drain is not clogged but the user forgot to run the garbage disposal before running the dishwasher? Let's assume some water can drain through the garbage disposal so it does not overflow back into the sink but it does fill up the garbage disposal with water. Or it does backflow a bit into the sink but the user never sees it. When the dishwasher pumps the waste water out, the waste water fills up the garbage disposal. Now the dishwasher's drain hose is full of water, the garbage disposal is full of water and the dishwater stops pumping. Since the drain hose is full of water, it acts like a siphon and will suck waste water from the garbage disposal, along with bits of garbage, back into the dishwasher. The high point loop in the drain line will NOT stop this from happening!

DRAIN LINE HAS AN AIRGAP INSTALLED:
If an airgap is installed in the dishwasher's drain line, waste water from the sink's drain or garbage disposal can never backflow into the dishwasher.

I encourage you to reinstall that airgap (on top of the sink, not under the counter). Also insure that the opening in the airgap's cover always faces toward the sink so if a clog in the airgap or dishwasher's drain line occurs, the water will be directed into the sink.

HRG

Very well explained but now we go into a different area some of opinion some technical, that’s what it’s called but technically it’s a vacuum breaker stops a siphoning action , air gap stops bacterial cross contamination which this device will not) here we cannot install a dishwasher gap valve in an appliance in a 2nd floor and above, Why? Because they fail and are unreliable, more often than a little dirty water in your dishwasher from a stoppage the home owner walks into a flooded kitchen full of dish water from a failed valve especially the cheaper ones like the one pictured. Some of the higher end units seem to hold up a bit better but our local code still applies. Most new machines come with the drain line already looped and it’s not even necessary looping it under the sink (code approved).. Again personal choices I personally loop it again. Again you are technically correct but he’s better off getting rid of the thing in my opinion

If your line is looped to the bottom of the countertop and you get waste backing up to the very top of your kitchen sink, you're going to have more serious problems than just the dishwasher having some scum inside of it.

:001_unsure::blink:

I have never been called out to get food out of a dishwasher, and I've lost count on the number of times I have fixed, cleaned or replaced airgaps. I'm not required to install the worthless things and you can't convince me they have any value.

The way this forum has always worked is for folks to respond to questions with their personal views and suggestions. All I did was to state my viewpoints and encourage the OP to reinstall the airgap. No need to take anything personally as that was not the intent of my post.

Best regards,
HRG

Likewise, I was only stating my opinion and experience with them.
My state does not require them. Not sure of the Plumbing Board's reasoning but if they write the code to protect the health of the nation and they deem DW airgaps are not required then thats good enough for me. :thumbsup:
If your AHJ wants it- then comply. I really don't care.

hrg good detailed explanation and easy to understand. but like the expansion tank forum a lot of different idea's and code differences.
i too do not use them though and not required but i do believe what you say is accurate.
i look at it as that is the worst case possible and when it backs up into dishwasher where clean dishes are and you get sink unclogged and then you go to put dishes away out of washer and open door and you see dirty water in bottom of washer you say huh got to rewash these too .

Hi jaydevries,

Thank you for your comments.

I think the clogged drain scenario is a worst case, but not clearing the garbage disposal prior to running the dishwasher might be a fairly common occurrence. Since dishwashers work by recycling the water in the bottom of the dishwasher, I don't want waste water from our garbage disposal being recycled on our dishes. (When I clean our garbage disposal using a toothbrush once in a while, it's pretty cruddy in there, as all drains are. :sick:)

As you mentioned, code differences allow installations without airgaps and folks have formed different opinions about their usefulness. That's fine and is as it should be.

Thanks,
HRG