Dishwasher Venting

[Bruce Page]

Is there an alternative to the dishwasher “Air Gap” cap that is normally mounted to the top of the sink (at least here in NM)? We are going to do a complete kitchen remodel and LOML has said that she does not want that chrome knob sticking out of the new sink.

[Jerry Bruette]

I'm pretty sure the local green BORG sells a soap dispenser that doubles as the air gap unit.

Jerry

[Mike Henderson]

You probably aren't having this inspected by the local code people, so I think you could mount the air gap under the counter top. Just be aware that if there's a clog in the drain, things will get wet.

Mike

[glenn bradley]

No problem . . . just skip the dishwasher . I am no plumber but, have seen a 'high loop' used instead in homes that happened to be about 25 years old in SoCal; newr and older homes may use them as well(?). I have no idea if the requirement is regional, functional or maybe 'ease of install' driven.

[Bruce Page]

Glenn, I'm the dishwasher filler upper so that won't work! Looking around on the net, it looks like some new dishwashers no longer require the external vent. I'll have to check if the new KitchenAid we have on order has it. The above the drain-level loop is also common.

[David Helm]

Air gaps or high loops are required by most AHJs. The idea is to keep dirty water from being drawn back into the potable system. For a high loop to work, it has to be attached to the underside of the countertop so the loop is above any water in the DW. The high loop acts in the same way as the air gap. It is an antisiphon device. The good news is that some dishwashers (usually higher end European ones) have a built in air gap.

[Von Bickley]

Bruce,
I have been around a lot of homes being built in central SC, and I have never seen a vent cap like you mention.
The kitchen drain is vented thru the normal plumbing and the dishwasher is just connected to the drain under the sink. No special vent cap.

[Mike Null]

Bruce

I retired from the appliance manufacturing business and never saw such a thing. (on our products or any of our competitors)

In most cases that drain hose is connected to the disposer.

[Mike Henderson]

Bruce

I retired from the appliance manufacturing business and never saw such a thing. (on our products or any of our competitors)

In most cases that drain hose is connected to the disposer.

It's required by code in certain areas. Your area may not require it.

Mike

[David G Baker]

Haven't thought about the air gap for years. My dishwasher does not have one and didn't have on inclided with it or mention it in the installation instructions.

[Bruce Page]

Every place that I have lived that had a dishwasher has had the sink top vent, I sure want to ditch it with the remodel. I like the idea of the high-loop David describes, it sounds easy enough to do.

[Matt Meiser]

Neither our first house or this house had one. Both have kitchens build in the 90's. My parents did in their 1960's kitchen but its gone after their remodel. All just have the high loop under the counter. I assumed they were no longer needed with modern dishwashers.

[Dave Ogren]

I just put in a new dishwasher (Kitchen Aid) about 5 weeks ago.Here the code only requires that you use a S.S. braided intake hose.
Good Luck,
Dave

[David Helm]

I guess I'll say it again. It is not a vent. It is an antisiphon device that prevents dirty water from being drawn back into the potable system. It doesn't come with the appliance. It is a separate purchase. Most dishwashers installed without it are installed by the homeowner who doesn't know about the requirement. They have been in the code for quite a few years.

[John M Wilson]

It is an antisiphon device that prevents dirty water from being drawn back into the potable system.

On my dishwasher, the discharge line (which is the one that you show with the antisiphon vent on the drawing) is completely separate from the water supply line.

The potable water supply opening is on the side of the dishwasher, about an inch above the bottom of the door opening, which would be the maximum high water mark of the tub.

The drain is in the bottom of the dishwasher. There will always be an air gap between the supply line and the drain line -- it's just internal to the dishwasher. Backflow into the potable water system would seem improbable, if not impossible.

I think perhaps the antisiphon is to prevent the dishwasher from siphoning dirty water out of the sink (or garbage disposal) back into the bottom of the dishwasher, thus rendering your clean dishes dirty again, or causing a nasty overflow/spill.

While I can't speak to code, which varies so much from place to place, I do think that your assertion that most dishwashers are installed by homeowners might be overstating it a bit. I have been in many, many new construction homes over the last few years, where the dishwasher was not installed by the homeowner, presumably built and inspected to code, and have seen an air gap in none of them.

The only places I have seen air gaps is in homes that had the dishwashers installed prior to 1980 or so...

Is it possible that the manufacturers made a design change and eliminated the need?