Do dishwashers need drain hose to rise above level of drain pump?

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I have a dishwasher located in an area where there is no pre-existing plumbing (ie - no sink nearby).
I've brought the water supply from the basement directly below the dishwasher through a hole in the floor. I've routed the drain hose from the pump directly down through the floor and connected it to a 2" ABS drain pipe that runs at a slight down angle for about 10 feet and ties into the existing drain system from the kitchen.
Normally I think that it's expected that the drain hose runs up above the level of the drain pump for maybe a foot before it ties into a nearby sink drain pipe.
But since I have my hose running down immediately when it comes off the drain pump, I'm wondering if I might have some siphon action going on whereby the water always has a tendency to drain through the pump even if the pump isin't running - because I don't think that manufacturers would install an electric cut-off valve to prevent water from draining when it isin't supposed to.
Comments?
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Sum Guy wrote:

How about using more drain hose and putting a big loop in the drain hose so it rises before going thru the hole in the floor. Also might help control sewer gas??
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Most dishwashers require the drain hose to loop to a level higher than what the highest possible operating water level. Read your installation manual for your dishwasher.
Some may require an air gap. Read your installation manual for your dishwasher.
Some have maximum lengths for the drain hose. Read your installation manual for your dishwasher.
You will find the answer to all of our questions in your installation manual for your dishwasher.
Why do people ask questions to strangers that they themselves could answer by doing a little reading?
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Gordon Shumway wrote:

This is a 14 year-old dish washer. I don't think I have the manual any more.
I thought I was asking a question that would apply to all dishwashers.
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Did you go to the manufacturers web site and see if an installation manual was available for download?
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My dishwasher uses gravity drain to the basement washtub. This was a quick temp fix 14 years ago till we put in a new kitchen which never occured. The dishwasher has been replaced twice over the years.
I have a drain loop as high as the top of the dishwasher top to prevent siphoning t works fine
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snipped-for-privacy@aol.com wrote:

That's what I suggested:-))
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== Yep, way to go. ==
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You do realize you just contradicted yourself. <g>
Why not? I get plenty of really good advice here. I don't take the advice literally but I often get steered in the right direction. Also, the process of writing the question out probably helps me more than the answers.
This is a sounding board. The problem you have is always a problem someone here has already been through. Bouncing ideas here and elsewhere is priceless.
Have faith in the common man and remember the choice is always up to you and you won't go wrong. If it seems like a stupid idea, it probably is, and if it seems like good advice run with it. :-)
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What might happen if the the existing drain system from the kitchen gets plugged up. Is the sewage entering from a higher source going to start backing-up into your dishwasher and onto the floor?An air-gap prevents this from happening.
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Air gap is code in some places. OTOH, I've not had one in either of my houses, a total of 40+ years and never a problem.
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On Fri, 30 Jul 2010 19:48:36 -0700 (PDT), Molly Brown

Does it really?
An air gap is meant to break the siphoning action by allowing air to fill what would otherwise be a siphon.
But with his suggested design and your suggested clog, it's not a matter of siphoning. The water from above, including toilet sewage, would stop at the clog, then go up the dishwasher hose to the anti-siphon**, then a little will squeeze out the anti-siphon hole and the rest would continue its route to the dishwasher, work its way through the pump blades and end up in the bottom of the dishwasher.
**And up any other pipes available also, like the one to the bathtub, the shower, the sinks, if they connect before the clog.
The way to avoid this is to not have clogs. I've been here 27 years and never come close to a clog, and I never had a clog anywhere else I've lived either. Because I don't let anything unusual go down the drain. But i"m not saying a conscientious person can't have a clog. I just don't know how it could happen.
If it ever does happen, he'll have to run the dishwasher through a couple cycles empty to clean it out. That's a lot easier than cleaning up a dirty overflowed toilet. (but not much harder than cleaning out the bathtub) If the mechanism permits, he can speed it through the washing and rinsing part since it will all be mixed with water already anyhow.
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Ive personally seen a house in a very affluent neighborhood of California where the sewage from the street backed into the first floor and completely flooded it and believe it or not the first floor was about five feet higher than the street outside. Apparently this house was somehow last in the sewer line coming down from a very slight slope that apparently didnt have an outlet or house for more than five feet of rise. I had to pop open a clean-out outside so that at least the sewage ran into the yard instead of the house until the city could come and snake out the street from the manhole. .
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Do you mean, While you are washing the dishes, the water will be draining, since it won't require a pump to drain?**
So if the water is draining while you're washing, new water, not yet heated by the dishwasher, will be added to replace the water that has drained out, and sometimes the dishwasher may pause if the water level gets too low, until it goes up again. But I sort of think the water can't drain during the wash and rinse spraying cycles, because the pump that handles the draining is redirected to handle the spraying. What about pauses, like the filling stages? Would whatever directs the water to either spray or drain keep it from draining during the fill stages? I guess the answer might be found in hallerb's post, but he has a full heigbt loop. So I"m still curious.
If this is what you mean, it's not really siphoning**, which refers to going uphill on its way to going downhill. For example, siphoning from a gas tank requires it to up the hose from the tank to the outside, and then downhill after that. That it can do this is the "mystery of siphoning".
But except for the footnote**, you're just talking about going downhill. That's called draining. :-)
Even if you're talking about the toilet draining from upstairs getting stopped by a clog and then going up into the dishwasher, I think that's called water finding its own level. I wouldn't call it siphoning. Although it took me a while to realize this. I was also influenced by the anti-siphon thing on the sink.
**Or do you mean that there is a trap in a normal dishwasher and if you drain down, it will siphon the water out of the trap. I don't think it's called a trap or built like a trap , but even if not a trap, some water is left inside the dishwasher all the time that the pump doesn't normally expel. There is such water aiui, but it's not needed to stop sewer gases normally, because the normal output of a dishwasher is to the sink drain above the sink trap. So the sink trap stops the sewer gases.
Is the drain you plan to connect to, is it above a later trap, or are there no more traps before you get to the sewer? If there are no more traps, yes I think it will drain the water from the dishwasher (whether that is called a trap or not.) and the sewer gasses will come out through the dishwasher. (In the other post, I was only arguing some more about the term siphoning.
If you put in a loop, woudl that be sufficient? Doesn't there need to be an anti-siphon device, or indeed it would siphon.
IIUC, if you put in a loop, the inside bottom surface of the hose would only have to be as high as the water level when the machine has finished its cycle, or at most the surface water level while it is running, which isn't that much higher, but I think others said it had to be higher yet or at least theirs was higher.

I doubt they would, and regardless of whether you still have a problem, I'd be interested in knowing what would happen if the drain goes straight down.

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Sum Guy wrote:

What happens when you try your configuration?
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I would be first concerned about whether or not there is a trap. From the description, it sounds like it's a direct connection to a sewer pipe. If so, that;s a code violation and could allow sewer gases to enter the dishwasher.
If you have a trap with a proper vent system per code, and the end of the dishwasher hose goes into the trap like a washing machine hose would, ie it's not sealed, then I don't think you have any problems. If the sewer backs up, the water will come out where the hose enters the system and not go up into the dishwasher above.
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On Jul 31, 7:38am, snipped-for-privacy@optonline.net wrote:

== If he continues to build it as he described, he will seriously compromise the sanitation of the dishwasher AND of the sewage system. Best he get some expert advice and most likely qualified plumber as well. ==
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Roy wrote:

You are correct - there is no trap between the dish washer and the sewer line the way I have it right now.
Although I've never smelled anything strange in the dish washer, probably because there could always be some water sitting in the pump acting like a barrier preventing a direct airway connection to the sewer line. Or the pump's impeller is enough of a barrier to prevent airflow.

I'm not afraid of a sewer backup. We have a separate storm-water sewer system that's not tied into our sewer system, and we're sitting on a higher elevation (relatively speaking) compared to other parts of the city. We don't have sump pumps in our basements either.

Hydraulically speaking, I'm not concerned about backflow from the sewer to the dish washer.
But I am curious about your concern about comprimising the sanitation of the sewage system. Could you explain that point a little more?

I can't believe that something as simple as whether or not a dishwasher drain hose must always form a loop (inverted trap) wouldn't be more well known if it was common knowledge.
For example:
http://lgknowledgebase.com/kb/index.php?View=entry&EntryID072
Note that in every diagram, the peak of the hose rises to the highest level as close to the top of the sink as possible.
I'm not sure what that do-hickey is in the last diagram - identified as an "air gap" that seems to protrude above the counter top. That can't be a desirable thing to have poking through your counter-top.
This video:

http://www.youtube.com/watch?v=S_0OWuFVLNw

explains how sink drain water can run back into the dishwasher.
In my case, I'm providing the dishwasher with it's own large 2" drain pipe that connects directly to one of the main 4" vertical lines that drains a bunch of fixtures from several rooms (probably about half the house).
If that 4" line ever backed up to the level of the top of my basement ceiling, then another foot higher it would reach the level of the bottom of my dishwasher, then another 1/2 foot higher it would reach the level of the bowl of my main-floor toilet, and then another 2 feet higher the backup would start filling the kitchen sink.
So if I was ever worried about a sewer backup into the dishwasher, it wouldn't take much more to backup my ground-floor toilet bowl (I don't have a basement toilet or sink, but if I did, then they'd backup before my dishwasher would). I do have a basement floor drain near my furnace where my AC condensate drains, but I'm not sure if that's tied into the storm sewer or sanitary sewer (probably sanitary sewer). So that would most likely backup before anything else would - unless the backup was caused by a plug in my main vertical 4" drain pipes.
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== Please talk to a plumber...he/she will provide the information that you need desperately. You are laboring under a load of miss- information and guesswork.
==
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Roy wrote:

Every post made to this newsgroup could be (non) answered with a similar statement.
Just change "plumber" to "electrician, engineer, contractor, lawyer, doctor" and you've covered 99% of all questions asked here.
In other words -
plonk.
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