I agree. Start with what the DW manufacturer says. Call them too. Dishwasher manufacturers know that all their products will send the drain water uphill a few inches (to a High Loop or to an AIr Gap). Therefore, I conclude, they have put pumps in that drain water by sending it that high as a normal course of operation. Therefore, I conclude, it might cause too much water to be drained if the drain hose is sent downhill upon leaving the DW instead of up first for a local high spot. Too much water being pumped out could mean the water seal is open instead of blocked by water. Plumbers will tell you that water dropping too fast to a P trap down too low can cause the P trap to siphon itself out, and this too can break the water seal, opening the line to sewer gases. The manufacturer will say something about this. Some will spell it out that the drain hose has to go "high " first before going down to the P trap, and some haven't written that out but will still say so over the phone. I'd call the manufacturer instead of relying on internet strangers. -david

What Miele did not tell people is the fact that there are two different types of Air Gaps described in both ANSI (American National Standard Institue)/ASSE (American Society of Sanitatary Engineering) 1006 / AMAM (Association of Home Appliance Manufacturers) DW-2PR-1986 (Section 3.1.1 Inlet Air Gap & 3.1.2 Drain Air Gap) and in 2010 California Plumbing Code (Section 203.0 Airgap, Drainage & Airgap, Water Distribution). They are for different purposes to comply to with the Codes. Inlet Air Gap is for âÂÂprevents reverse flow from the dishwasher to the house water supplyâ per ASSE 1006-1986 Section 3.1.1 Inlet Air Gap. Water Distribution Airgap is for âÂÂunobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet conveying potable water to the flood-level rim of any tank, vat, or fixtureâ per 2010 CPC 603.2.1 & 603.3.7. Drain Air Gap is for âÂÂprevents reverse flow from the house drain plumbing to the dishwasherâ per ASSE 1006-1986 Section 3.1.2 Drain Air Gap. Drainage Airgap is for âÂÂunobstructed vertical distance through free atmosphere between the lowest opening from any pipe, plumbing fixture, appliance, or appurtenance conveying waste to the flood-level rim of the receptorâ per 2010 CPC 603.2.1 & 603.3.7. MieleâÂÂs âÂÂinternal air gap of greater than 1 inch on the potable water supplyâ satisfies requirements in ASSE 1006-1986 Section 3.1.1 and in 2010 California Plumbing Code 603.2.1 & 603.3.7., but its âÂÂinternal check valve and air break on the waste dischargeâ does not satisfy requirements in ASSE 1006-1986 Section 3.1.2 and 2010 California Plumbing Code 807.4, because there is not such option described within the sections; in fact, it requires âÂÂthe use of an approved dishwasher airgap fitting on the discharge side of the dishwashing machineâÂÂ, which we can find the listing standard in Chapter 14âÂÂs Table 14-1 of 2010 California Plumbing Code âÂÂDrain Air Gaps for Domestic Dishwasher Applicationsâ per ASSE 1021-2001 !!!!! The provision in regards to domestic dishwashing machine has been published in Uniform Plumbing Code and/or California Plumbing Code for at least 28 years (the oldest version I found is 1982 Uniform Plumbing Code). The entire sectionâÂÂs text has never changed/revised with exactly the same words from first alphabet to the last alphabet including punctuation.

You are right. Sorry I didn't catch that, in the image. You cannot leave it that way. You already know most of the big reasons why not. If you need to read all the problems, find out about sewer gases. Some are lethal (but my saying this is not designed to give you nightmares). The DW connection has to go on the other side of the P trap. You can buy more hose instead of replacing that one. Radiator hose for car motors is good because it is smoother inside. The reason these cheap hoses are corrugated is to ensure they never collapse. A smoother inside wall can reduce noise quite a bit - not in all cases, as it depends on the flow and how you configure the geometry of the fall. HTH -david

Thanks @whirlpooltrainee & @nerdyshopper. I made an appointment with a tech from a Bosch-affiliated shop coming by at the end of this week. In the meantime, I had my regular repair guy (who'd cleared the problem last time) and he said it should have been high-looped (which is what the installation manual says as well). So he made that fix and reset the machine so that it works. But he also indicated that there was water collecting at the bottom of the tub and that he thought the control panel was wonky. I'm keeping the Bosch warranty appointment for this week to make sure that I get it fully checked by an expert.