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

Page 2 of 4  


== Fine, do it your way.
<double plonk> ==
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Apparently the OP is one, that when given good information, chooses to ignore it. I still wonder why they ask in the first place. I hope I never have a neighbor like that, trying to bring the property values of the neighborhood down, every time they pick up a tool.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Gordon Shumway wrote:

Where is the "good" information?
All this talk about code and traps and air vents is nice, but it doesn't speak to my primary question.
I want to know if dishwashers depend on having the discharge line rise above the level of their drain-pump outlet before the connection point to a drain pipe. This bit of plumbing may not be seen or noticed by most people since it can happen inside the machine's chasis or enclosure.
I happen to be routing the discharge line directly through the floor under the machine, and the drain-pump outlet is just inches above the floor surface.
I know I can route the discharge line up inside the enclosure for some distance (2 feet at least) before looping it back down through the hole in the floor. But I'd like to know if dishwashers depend on such an arrangement or not.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

== Well, a plumber can tell you that and more. ==
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Roy wrote:

So you're saying that I shouldn't expect an answer here from someone who might be a plumber - or who is otherwise well-informed or knowledgeable?
Why does this newsgroup exist, if the pat-answer to all questions (according to you) is to ask a (plumber, electrician, pipe fitter, roofer, brick layer, engineer, chemist, contractor, lawyer, doctor, ...) ?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

== Qualified electricians, plumbers, etc., keep up on these things because it is necessary for their job. I might remember what was up to code when I installed an appliance back in 1982, but many code changes may have come about since. I was not being a smart ass for suggesting an expert in the field of plumbing but perhaps to help you avoid an error which could cause financial or even health problems in the future. ==
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You have to admit, this thread has been running for a long time, and no one has answered your exact question. IIRC people have even disagreed with some of the things that were said.
I don't remember anyone here being a licensed plumber.

I think about 20, 25 years ago, someone wanted to discuss home repairs. Either that or someone just put it on the list, even though he personally wasn't interested.

But it's not the answer or an answer given to all questions. It wasn't even the only answer given in this thread.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You have been given the following "good" information several times:
1. RTFB.
2. Get professional help.
Your choice is probably going to be "3. None of the above, I'm fully capable of screwing things up all by myself".
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think looping high is neccessary. Also since you are going into the basement a air gap may be essential.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

In the drawing but the text says the minimum is 30 inches. I think in practice the easy place to put the air gap is at the rear of the sink.

Why not? I have one. It doesn't get in the way. The air gap is the whole point of it. That's what stops the siphoning**. BTW, I once had a little chicken bone, the one next to the drumstick, in the air-vent and the dishwasher would not drain. It took a while to find the problem, and I'm still not sure how this little bone kept it from draining.
**although I'll admit, I havent' figured out when there would be siphoning, or even in which direction. Stuff that would go into the dishwasher woudn't be siphoned in, I think. Maybe it is there to stop the water in the bottom of the dishwasher from being siphoned out????

I'll have to look at that.

Yes, the toilet would overflow first if the backup was in the 4" line.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[...] | 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.
One problem is that code requirements have changed over the years and dishwasher (cost reduction) design has taken advantage of this. My house's original dishwasher (~1959) was hard plumbed directly to a trap in the basement. It had no high loop, no air gap, and no standpipe. It did have a positive drain valve solenoid that closed the drain when it was not trying to pump out water. It was also wider than current dishwashers. As far as I know, that installation was to code at the time.
The first replacement dishwasher (in the 80's I think) was a KitchenAid and while it did not have a drain valve it did use a separate pump for removing water. It was happy with a high loop but still hard plumbed to the trap in the basement. I _think_ the installation manual showed the hard-piped trap as a valid (though not necessarily legal) configuration.
The next replacement (I don't remember the brand) in the 90's (notice that life span is decreasing :) did not have a separate pump for removing water. Instead it manipulated the circulating pump in such a way as to cause a little plastic flap in a chamber to divert water out. This appeared to depend critically on the back-pressure at the drain and I was unable to make it work reliably with the hard-piped trap, regardless of high loops.
I was able to find a different brand that still worked with the hard-piped trap, but I decided that that configuration's days were numbered so I reworked the kitchen sink setup with a garbage disposal. The latest replacement dishwasher has a high loop and empties into the dishwasher port of that garbage disposal per the current preferred configuration.
IMHO, in general, a high loop saves you only if the drain hose opens to air before it gets back as low as the highest water level in the machine. This is the case with the garbage disposal port but not with a hard-plumbed trap below the floor and not even with a standpipe below the floor.
[...] | 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.
As the name implies, it is a true air gap that both prevents siphon and diverts any reverse sewage flow onto your counter (which is arguably better than hiding it in the dishwasher). The aperture on the dishwasher side is smaller than that on the sewer side. This is currently the ultimate in safety and (I believe) required by code in some places. Something I'm not clear on is whether you can use an air gap and then hard-plumb the outlet to a trap under the floor. Somehow I think that even with the air gap you are supposed to enter a disposal or open sink trap.
                Dan Lanciani                 ddl@danlan.*com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sum Guy wrote:

As long as you are going at a continuous downward angle below the pump it will siphon out just fine. It's when they drain into the sink drain above the pump level that they need a loop above the drain level to get siphon action to completely drain the dishwasher.
--
LSMFT

Those who would give up Essential Liberty
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
LSMFT wrote:

That's the problem. I'm wondering if the water is siphoning out when it shouldn't be.
I can understand that the recommendation is that the drain hose make a loop going up to above the level where the sink water-line might be - to prevent the sink water from draining into the washer.
But if you don't have to worry about the drain from a sink (because there isin't one nearby) then do you still have to worry about water draining out of the washer when you don't have a rising loop in the drain line?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not sure I would make a direct connection to the drain in the basement. I would probably add a stand pipe with trap and air vent much like I was plumbing for a clothes washer. I would raise the drain to the dishwasher to just below the countertop before heading to the basement simply because every dishwasher install instructions that I've seen says to do it. Most instructions allow increasing the hose length if needed.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pat wrote:

It's conveinent.

(I don't have a countertop - this is a portable dishwasher that I've parked in the corner of the kitchen).
Do they recommend it to prevent the sink from draining into the washer, or because the washer needs the drain line to go up first before it's connected to a drain pipe because it can't stop water from siphoning out by itself.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Your lights go out because a 15 amp fuse blows. Following your logic, you put in a 30 amp one because it's convenient. The lights are back on. Problem solved.
There is a reason why code requires a trap and vent on drains. Several people here have tried to explain to you why what you're doing can and likely will result in sewer gas entering the dishwasher and living space. But that doesn't concern you.

Going up first doesn't stop a siphon from working. I can place one bucket of water 15 feet higher than another. Take a hose, fill it with water, put it in the high bucket and let the hose rise another 2 feet above the bucket. Put the other end in the lower bucket. The water will still siphon.
The high loop is there so that if the sink drain backs up, it will rise into the sink first and will only get to the dishwasher if it rises clear to the top of the high loop, ie as high as the bottom of the counter top. For it to rise that high is quite unlikely and someone will likely notice the backup, as opposed to it going unoticed and just contaminating the dishwasher.
But, why all the concern? You obviously don't care about doing plumbing to code when there is an obvious and very good reason for the code, ie a trap and vent to prevent sewer gas from coming into the house. The dishwasher seems to be working, so just do it your way.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@optonline.net wrote:

Replace the word "siphoning" with "draining" above.

I don't have a sink drain. The dish washer is not competing with a sink in this case. The washer is located in a corner of the kitchen away from the kitchen counter and sink. The dish washer is not sharing a common 2" drain pipe with an adjacent sink.
I've explained many times - I've arranged it so that the dish washer discharge line is fed directly DOWN from the drain pump outlet through the floor to a dedicated 2" ABS line that runs at a slight down-angle for 10 feet to a connection on one of my primary 4" vertical sewer pipes that runs into my concrete basement floor.
If something backs up on that 4" line, then I've got more of a problem that could ever be solved by having a proper dedicated trap and vent for the washer.

Because my washer does not seem to be operating properly - it seems to need to have water added at times during the various cleaning cycles as if water is leaving it for some reason.
I'm wondering if the water is draining through the drain pump because there is no "up-loop" in the discharge line.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Likely. Also the sewer gases are coming up into your dishwasher and entering your house 24/7. The dishwasher is made to vent the air/moisture inside out into your house.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pat wrote:

Wouldn't my vent stack provide a lower-resistance path for sewer gas vs trying to go through the dishwasher's drain pump?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sum Guy wrote:

You can hook it up with or with out the loop. If it works without the loop good deal, if the water drains out as it fills then make a loop. I'd do the loop anyway, bugs have a habit of crawling inside and up anything they can and you might find a bug or two in your dishwasher someday, if there is an air gap to the floor drain in the basement there shouldn't be much chance of sewage contamination. If you and your family are healthy a year from now, no problem! Me I'd want to make sure there isn't sewer gas getting back to the dishwasher. A trap as close as possible is the best way I know of to do that and the machine gets plenty of hot water (that is really good at killing or reducing germs) and dissolving fats. FWIW I always throw in some water in before running my dishwasher, lubricates the seals before the water gets around to flowing in, starting the dishwasher dry is a good way to shorten it's life. I also turn on the hot water at the faucet to get the hot water at least that far, then shut off the faucet so the dishwasher can start with hot water coming in. And finally the purpose of requiring licensing of plumbers is to protect the public water supply. It is possible that an incorrectly installed dishwasher (or anything) could be contaminated with sewage or chemicals, then an improperly connected water supply via the plumbing can back feed to the public water system causing contamination of the public water supply system. It usually takes a chain of events for this to happen but it does, nail, shoe, horse, soldier, battle kind of thing. google "water supply cross contamination" if you are interested. There are lots of examples of this happening. You just might be drinking your neighbor's sewage or the chemicals he sprayed on his lawn. Now go forth and get the dishes washed. What are wives good for anymore? Aren't they supposed to wash the dishes?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.