I was installing a dishwasher for a friend of mine this evening and while looking through the directions it made no mention of a high loop. An air gap diagram was present but it said only required by AHJ or local codes.
According to WHirlpool there is no need for a high loop…
Any comments?? 
What was the retail price of the unit?
It seems that the ones that cost over $500-$600 have the high loop built in.
Some models do not require them.
Pretty is to do if not sure.
ThisWhirlpool Manualdoes.
Drain Requirements
■ Connect drain hose to waste tee or disposal inlet above drain
trap in house plumbing.
■ Connect drain hose to house plumbing 20" (50.8 cm)
minimum above the floor.
NOTE: It is recommended that the drain hose either be looped up
and securely fastened to the underside of the counter, or be
connected to an air gap.
■ Use a drain air gap if the drain hose is connected to house
plumbing lower than 18" (45.7 cm) above the subfloor or floor.
Drain Air Gap
And so does theirmost expensive model, $999.00
http://www.whirlpool.com/catalog/category.jsp?Ns=PRODUCT_PRICE|1&N=0&cat=108
Theres that dirty word again. . It is recommended but not required…
BTW it was a cheap model. quiet partner 1 i believe…
SO unless its a code for an air gap it aint a requirement only a recommendation.
If the IRC applies in your area a high loop is required.
My understanding is that with most dishwashers if you dont have the required high loop (or required air gap for places still on UPC based codes) on the discharge/waste line, the sink can back up into the dishwasher … :shock:
P.S. In addition, the supply line needs to be protected by an air gap or backflow preventer, which is usually built into dishwashers. Perhaps the mfr meant an air gap on the supply isnt needed.
How long does it take to install a clamp and anchor the flexible drain line beneath the counter? Maybe 2 minutes… maybe less? Sure is a helluva lot less time and effort than gets invested in determining whether it’s required or recommended…
My opinion… who cares whether the jurisdiction requires it or not… just do it!
prolly no requirement for a toilet seat either…do You want one or not?
Digging up this old thread because I got a call to explain what I meant by "Dishwasher does not have a sufficient high loop to prevent drain water siphoning back into dish washer unit.
I have called this out many many times and have never had to explain what I meant.
I provide a photo of the defect and include an arrow demonstrating where the loop should be mounted.
Just wanted to share than no matter how clear you think you are, sometimes someone will not understand.
I know some models do not require a high loop as they have an air gap built in but I call them out every time I see them under the sink.
It’s such an easy fix I am surprised anyone cared.
Saying from a Murphy’s Law calendar given to me by the mother-in-law, herself a Murphy:
“No command or order is so simple that it cannot be misunderstood”
I include a picture of the drain hose in every report.
Must be more wast of time the 10 page report guys all hate.
I posted a while back about the loop, because I have been seeing New homes without the loop, seems like the same models with integral back flow preventer. spoke to a plumber who claimed he had been installing without a loop for a while .
Just curious what models have a built in air-gap on the discharge, becuase I havent come across that yet. Many have built-in protection on the supply side, but not on the discharge side. Are those special models for areas still on UPC codes (like CA) that require an air gap instead of a high loop on the discharge?
Recommend airgaps however a high loop is acceptable to me.
You have no way of memorizing so just do yourself a favor and recommend for all.
Easy to do and an argument is a waste of everyone’s time.
I write it up every time. But I also teach home inspection, so I like to be aware of exceptions to the rules … 
It’s integral to the machine and not observable.
This active rain post is very helpful for those wanting to gain understanding.
That talks about a built in loop (not a high loop) … which is also not a built in “air-gap”.
Did you mean they have a “loop” built in? Thats different than an “air gap”. I am aware of built-in side loops and water supply protection, but I am not aware of any that have a built-in “air gap” on the discharge side.
http://cascadebuilderservices.com/images/airgap.jpg
http://www.plumbersurplus.com/images/prod/5/Danze-D491342SS-rw-61963-135485.jpg
I misspoke Robert.
I know of no units with a built in air gap only the high loop at the back of the machine.
I write it up if i can not see it , simple and easy
Exactly