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No Air gap for Dishwasher

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136K views 31 replies 18 participants last post by  stp57  
R
#1 ·
I was helping a friend remove an old countertop yesterday in preperation for a new counter top and sink install in a few days. We got to talking and he told me that the counter people told him he did not need a whole drilled for the air gap. They told him he did not need an air gap. Is this true? I have only hooked up a few dishwashers in my day, but I have always used an air gap. I'm thinking that without one, water could backup into the sink when the dishwasher drains. What's the real deal with not having a air gap?

Thanks

Rob
 
T
#2 ·
I'm not an expert and probably full of hot air but,

I installed a new dishwasher in my kitchen where one had not been before. My cast iron sink was relatively new with no hole for an airgap.

A plumbing friend of mine suggested the following:

When running the drain line loop the drain line inside the cabinet before connecting it to the drain pipe. Making sure the loop is up as opposed to hanging down. The loop in mine is about 16" in diameter.

Works fine, have had zero problems with the dishwasher draining or any water backing up onto the sink.
 
M
#7 ·
I've installed a few hundred + dishwashers and very few with air gaps, in the City of Chicago it is/was a requirement but we never installed one (eliminated quite a few), only hooked up existing ones. The IPC requires them, the UPC does not and I don't know about the Illinois plumbing code. Way to many codes relating to this. The purpose of the air gap is too prevent back-flow and siphoning, and newer dishwashers (past 20 + years) have back flow preventers built in and looping the drain hose (not a circle, but an upside down u to the top of the cabinet or behind/side of dishwasher) prevents siphoning. Aside form being ugly space wasters the cheap air gaps have a tendency to spit and cough water out.
 
M
#14 ·
No, even with the side loop you still need an air gap. It is the opposite of that, it is so a backed up sink does not follow into the dishwasher. I'm not a plumber but for this type of question visit www.plbg.com. Ask for HJ, Redwood, dlh, or packy. As far as plumbing goes you will not find a more definitive answer and those guys are infallible.
 
N
#16 ·
Air gaps haven't been required here in years and I refuse to install one. Te purpose was to prevent a cross connection between the water supply and the waste. On the old dishwashers the supply line entered the dishwasher below the flooe level rim or in plain english the botom lip of the door. The new ones now fill from about 4 inches up on the side therefore creating an air gap within the dishwasher.
 
J
#23 · (Edited)
oh really.

I put a bottle brush down the air gap. Problem fixed......There was a plumber who came up with the idea. He put it on a video in cyberspace somewhere. His other idea is to use a wet vac. He seems to think that will work. The other thing is the notion that this water is being evacuated at high speed, and so one's drain may need snaking.

But hey, thanks for the professional advice.
 
J
#28 · (Edited)
and obtw, ron, the plumber did not fix this the first time around. So I wanted more insight into the problem. The Garbage disp is brand spanking new, as is most of the kitchen, thanks to the rest of the crew.

To those who have no idea what this is about due to the untimely deletion, water started coming out of the air gap for the DW. Pipes and GBGD seemed clear although there was some debris in the air gap. It was finally fixed with a bottle brush in the air gap itself.
 
D
#29 · (Edited)
The Correct Answer

This seems to be a never-ending debate, so I’ll finally try to put an end to it. I have been a plumbing/ mechanical inspector for 23 years and the code has not changed requiring a dishwasher airgap the entire time.

I am speaking of the Uniform Plumbing Code (UPC) published by IAPMO. There are other plumbing codes which some jurisdictions have adopted, but the UPC is the most popular, however most states and local jurisdictions do make some changes to it, and the DW air gap requirement may be one.

The only sure way to know is to call your local jurisdiction, but even in my office, this issue is sure to raise a fire-storm of debate. Many inspectors ignore the requirement while others enforce it. Most of the points made on this thread for reasons not to install are valid, but nonetheless, the requirement remains.

The latest edition (2009) of the UPC 807.4:

“ No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher airgap fitting on the discharge side of the dishwashing machine. Listed airgaps shall be installed with the flood level (FL) marking at or above the flood level of the sink or drainboard, whichever is higher.”

The reason for the requirement is BACK-SIPHONING. This may happen if there is blockage in the waste line down stream of the sink and the dishwasher discharges and backs up into the sink. This standing water in the sink could siphon back into the dishwasher when the cycle is complete. I have personally seen this happen on many occasions, especially in older homes with smaller drain piping, and with older dishwashers. This is a real possibility with any home and any dishwasher without an airgap.

Beware of the plumber who says “I’ve been doing this for 10/ 20/ 30 years and NEVER used them or had a problem.” (I’ve heard them all) What they are REALLY saying is that they have never had a call-back. BIG DIFFERENCE. No plumber revisits all of the houses that he has plumbed every few months to see if everything is working properly.

I personally don’t see the need for an airgap fitting on a modern dishwasher, but there is no universal requirement that dishwashers be built with a foolproof back-siphoning system. Yes, they are unsightly and spit water all over and are routinely removed by plumbers and appliance installers alike, but it should be your choice, and make it on reliable information.
 
D
#30 · (Edited)
I suppose it could still happen due to gravity. I know that all of the dishwashers I’ve serviced for probably the last 30-years have either some type of a normally closed, solenoid operated drain valve or built in flapper type one-way check valve. As I recall, even the old Kitchenaid dishwashers from the late 1950’s or early 1960’s even had the drain solenoids.

 
U
#31 ·
If the code requires something, you have to install it that way. Your professional experience does not override the duly created building, electrical, or plumbing code.

Remember that your license is granted by a government body, and that when you practice your trade you are acting as a representative of that body. You have an obligation to meet the minimum requirements of the code. Anything else, and you are remiss in your responsibilities, no better than a handyman.

Keith
 
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