Miele Dishwasher install

hobbes778December 12, 2008

I am installing our Miele Inspira since our builder provides the rough-in. I noticed that the Miele has a large diameter drain hose (7/8"). Where the rough-in is a small barb maybe 1/2" diameter? Is it ok to put a reducer of some sort to attach to the drain?

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If the machine will drain through a garbage disposer, the inside diameter of the drain hose should be the right size to simply slide over the drain nipple on the side of the disposer (don't forget to punch out the slug in the nipple, first). Miele dishwashers don't require a connection to an air-gap, they have a built-in anti-siphon device. Simply bypass the air-gap, and connect directly to the disposal. Miele specifically advises against connecting the drain line to an air-gap or restricting the drain line in any way. Doing so could cause warranty problems, and very likely will shorten the life of the drain pump.

    Bookmark   December 12, 2008 at 6:28PM
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Every DW still needs a high loop even if it has that device.

Call Miele about its DW drain.

Drain plumbing needs to be all of the same diameter or larger, never smaller. In the Plumbing forum plumbers will confirm that for you.


    Bookmark   December 12, 2008 at 6:33PM
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What ever you do don't cut any the hoses. If you cut the drain hose the DW will not work because it has electronics in it that help detect leaks.

I don't think Miele's require a high loop because they are able to hold the water in and will not let water back into the machine. I've had two machines one for 10 years and this current one for 2. My DW drain hose goes directly down through the floor and connects to the drain in the basement. No operation problems with this.

    Bookmark   December 12, 2008 at 11:09PM
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Davidro1, You are mistaken. Miele dishwashers have a built-in anti-siphon device. They require neither a high loop, nor connection to an air-gap.

    Bookmark   December 13, 2008 at 12:22AM
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jerrod - you' re advice is sound: don t cut the hoses on a Miele DW. However, for the sake of accuracy the dishwasher WILL work if the drain hose has the end cut off of it. It doesn't have any electronics or wires in it like the supply line does. You'll likely encounter warranty headaches if the cut is discovered during a call and Miele didn't sanction the modification which is VERY unlikely.

    Bookmark   December 13, 2008 at 2:24PM
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Thanks for the correction antss. I checked my DW manual and there is no restriction about cutting the drain hose. I guess I had it in my mind not to mess with any hose. The manual does recommend ordering extensions and adapters from Miele.

    Bookmark   December 13, 2008 at 4:01PM
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Thanks for the input. Seeing as how I couldn't find any nice way of connecting the drain hose anyway, I think I will put in a larger (3/4") tee into the drain. Hopefully I can connect to this drain plug better. They don't seem to have any 7/8" tees.

    Bookmark   December 15, 2008 at 4:31PM
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High loops are for public health and safety, not for the benefit of the dishwasher. Air gaps are one step greater protection for the same purpose.

Even with a backflow stopper.


    Bookmark   December 15, 2008 at 4:46PM
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How is public health and safety likely to suffer without a high loop or an air gap? The purpose of an air gap or a high loop is to prevent water in a stopped up house drain or drain line from being siphoned or backing up into the dishwasher. With an anti-siphon device built into the machine, the same utility is achieved.

If by 'public' you mean the municipal water supply, then your reasoning is somewhat flawed. In every dishwasher I've ever seen, the fill inlet is high enough in the cabinet interior, that it would be impossible for backed up water to reach it. The kitchen floor might get wet if the sump and dishwasher bottom were to overflow, but the municipal water supply would still be safe.

    Bookmark   December 15, 2008 at 7:00PM
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When a DW drains through the floor into a drain in the floor level below, a high loop is not necessary, as far as I know. This is in reference to a previous post far above.

About the fill inlet in the cabinet interior, there is so much that I could say but I think it is best to wait until someone else who can say just the right number of words (only a few well-chosen words might explain it very well). Let a real plumber who is articulate speak up. Let's go to a plumbing discussion forum like terrylove.com/forums/ and see what they say. In gardenweb I have seen a plumber whose handle is lazypup: he is articulate and he seems to be able to say precisely what is needed to express all that needs saying and only that. Total precision.

Rules regulations and laws exist regardless of any discussion between wa8b and me. Other people more expert than either of us have given this a lot of thought before we began to.

Regardless of the purported reliability of a manufacturer's device, drain water (and contaminated water) can flow back through it. I think we can all agree that Devices can fail or work imperfectly. At the very least let's agree on that right away. I think then it may be instructive to know of other (rare) circumstances under which a device can be forced to fail, like e.g. a total blockage of the sink drain that lasts for a long time, which puts the device under pressure.

Gravity is foolproof and this is what high loops use to make them work. Air gaps are even more secure and that is why they are required by code in some places. Many people wonder why air gaps are required in some places while other require high loops only. Search on "cross-contamination" in plumbing forums and read what plumbers have to say.

Let us not encourage people to rip out code-required structures just because one of us might think it is not really all that necessary. What we think of how often devices fail and how often we think people die from the water supply is not a subtopic that I would find appropriate for this thread and for the two of us right now.

No Dishwasher requires a high loop to drain itself as far as I know. I doubt Miele would ever say that you should disregard plumbing codes or that plumbing codes are silly. To drain a DW, a high loop is not required, but to respect laws that have public safety as their focus, Miele would probably say yes you should. No DW needs to drain through a high loop. Also true is that no DW manufacturer will guarantee that no slippage or leakage will ever occur and ask for an exception to the law just because they feel confident in their current product. There is too much liability at stake.

Let's open a new thread somewhere else about all this.

The fill inlet in the cabinet interior is not the thing at issue here. Let's get a plumber in to explain it totally perfectly without any possible misunderstanding. Preventing contamination in the water supply is not my professional field so I think I have said enough for now.


    Bookmark   December 16, 2008 at 5:32PM
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Sorry David, but just as you were in your post last month about dishwashers humidifying the underside of kitchen counters, you're in over your head here, too. One has to wonder how you hatch these strange theories.

No one is advocating violating plumbing codes and no municipality that requires an air gap is going to allow a high loop in place of an air gap. Gravity has absolutely nothing whatever to do with any of this. Air gaps prevent back flow through siphoning, which can take place regardless of gravity, or the lack there of.

If public health were at stake, the national plumbing codes would require air gaps, and all communities would have to conform. The fact is, many communities have no such requirement, and I've never heard of any community requiring just a high loop.

We don't need a new thread. What would be the point? It's very clear you're way out in left field on this topic -- and some others.

BTW, how many dishwasher installations have you ever seen that drain to the floor below?

    Bookmark   December 16, 2008 at 9:19PM
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I'll take a few pictures and post them onto that thread about humidity. I referred to humidity not draining onto the floor. Meanwhile lay off please.


    Bookmark   December 16, 2008 at 9:57PM
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David - gravity dies fail. How do you think man got to the moon or gets cable TV? Likewise I could create a scenario in which a high loop can fail too. So what?

In some instances a high loop makes sense, in others anairgap is the only choice, others a mechsnical valve is great. Espousing one over the other in all instances only makes you look like you have a hidden adgenda or are merely being obtuse. The engineers at miele take their craft seriously, that's part of the reason they are the only one with a check valve. They can also command the pricing to make it's cost viable.

How are you going to accomplish a high loop in a old Eastern Seaboard home in which the DW hose goes directley out the bottom of the unit NGO the cellar?

    Bookmark   December 16, 2008 at 11:26PM
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