"... is it acceptable to create a high loop for the dishwasher drain line by passing it through a high hole in the cabinet, or is it necessary to use a low hole in the cabinet and then use a strap to make the high loop?" AFAIK in areas where the high loop is permissible you start low then go high under the counter top and then down... hence the name high loop. Starting high then going down would not achieve the same thing as a high loop. I defer to those licensed plumbers on the forum for the final word. Air gap may be required in some localities or not and high loop may be permissible in some localities or not. It isn't what you want to do or what is easier or more convenient or what someone tells you is OK. If you want to do it right (according to local code) then check with a local plumbing inspector or look it up in the governing plumbing code yourself.

Chances are, the lack of an air gap isn't your problem. You don't say how old your dishwasher is, what type of detergent you're using, or how thoroughly you scrape dishes before putting them in the dishwasher. If this is a recent development with a dishwasher that has always functioned properly without an air gap in the past, then chances are, the lack of an air gap has nothing to do with your problem. If your dishwasher is getting old, then perhaps the drain pump isn't functioning as well as it once did, or you have an obstruction in the drain line. Have you checked to be sure that you don't have anything partially blocking the drain line or some obstruction in the port where the drain line connects to the dishwasher? Either could be the cause of your problem. There are undoubtably millions of dishwashers out there operating without air gaps while delivering perfectly satisfactory results. The air gap requirement in many municipalities is a fairly recent phenomenon, and does nothing to improve the performance of a dishwasher. If your dishwasher has been doing a good job without an air gap in the past, it should continue to do so. Food debris left behind on dishes is more likely due to an aging dishwasher with a failing soft food disposer, a drain pump that isn't functioning properly, or a partially clogged drain line. If you're sure the drain line is clear and your dishwasher is an American brand that's more than 8 or 10 years old, it may be time to think about a new machine. Consumers Reports says that a good rule of thumb is that it's generally not worthwhile to repair most major appliances that are over 8 years old. Should you decide to think about a replacement, you might be interested to note that most European brand dishwasher employ micro-screen filtering systems that prevent food debris from circulating in wash water sprayed thoughout the wash cabinet and being redepositied on the dishes. Most debris captured by the filters is sluiced out of the machine during the drain cycles, but you will need to periodically check and rinse the filter of any large bits of bone or bits and pieces that are too large to be sluiced out. Most American brand dishwashers, on the other hand, don't employ filters, but rely a grinding mechanism, called a soft food disposer, which pulverizes food debris into tiny bits so that it can be readily sluiced out of the machine in the drain cycles. In this system. pulverized food debris continues to circulate in the wash water, and can be redeposited on your dishes if it isn't completely sluiced out of the machine in the rinse and drain cycles I don't think an air gap is going to improve your wash results. Barring obstructions in the drain line or drain line port on your disposer, it may be time to think about a replacement dishwasher.

Okay, I checked out the terms for you: You have to have some way to prevent backflow. Some DW's (presumably inc. Miele) have a built-in check valve. You could instead install a "high loop" on the drain. Or you can have a visible airgap on the sink edge. Airgaps prevent the sink water, or anything that backs up in the line, from getting into the DW, same as high loops or check valves, and also give you a warning when you have a stoppage like in the picture above. Lowspark is right about people removing ones that are put in just for code, but they're not useless. If you have a check valve or high loop they're redundant and unnecessary. Otherwise, you really do need one.

Thanks. Those are great tips. Unfortunately, we don't have a garbage disposal. Never thought of it this time around - lots of stuff I should have added now that I think about it. We have loads of brass already in the pulls and lighting so I'm not feeling the need for a brass faucet (but love the look in some over the top kitchens). Oddly, I'm thinking of going back to our Moen Aberdeen. We had some trouble with it and had to replace some parts, but it really met our needs and I've read that Moen corrected the problems people were having with it. It's not the most glamorous faucet out there, but it kind of blends in and has a brushed sort of finish to hide those water spots. And, of course, the holes will fit!