Dishwasher in seperate countertop from sink

Hey Everybody,

I've just bought a house and am not convinced by the setup used to connect the dishwasher drain. I'm in the process of replacing the dishwasher and was considering a reconfiguration. I figure a picture is worth a thousand words, so a CAD drawing must be worth at least a few hundered words?

The current configuration, as drawn below, is the dishwasher drain has a high loop (33" up) then penetrates the floor before travelling about 80" horizontally before connecting to its own P-trap a total of 29" down.

I'm worried about the drop to the p-trap siphoning out the tub of the dishwasher through the high loop. The old dishwasher pump will whine once a cycle, perhaps from being siphoned dry?

I don't really want to install an air gap above the countertop, though that would get rid of the siphoning potential. I know usually the dishwasher drain should come in above the sink P-trap, but if i were to do that in this case i'd have an 80"+ length of tube with standing drain water in it. I'm a plumbing novice and open to any solutions (or people telling me i do not have a problem to begin with).

Dishwasher lists a min high loop of 33", max high loop of 43" and an aggregated maximum drain hose length of 150".

Thank you

Hello,


I suggest, you call the manufacture with model number and ask the max [head] length the pump will pump.
If I were at your house that is exactly what I would do first.

if manufacture says the pump will not work in your situation. then you will need to install a small sump pump
below the floor.

if manufacture gives you the green light. it needs to be plumbed with the loop under the sink cabinet not behind the unit.
I would also suggest you plumb the drain using either cpvc or copper instead of hose
see drawing.

My dishwasher is a 1/2 a cabinet away from my sink where it drains and I will tell you that extra length of the dishwasher drain is not a good thing. I constantly get foul smells from something down there. I just live with it.

PlumbGate said:

My dishwasher is a 1/2 a cabinet away from my sink where it drains and I will tell you that extra length of the dishwasher drain is not a good thing. I constantly get foul smells from something down there. I just live with it.

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How, exactly, is it tied into the sink drain line?
Is dishwasher drain hose looped, then tied into your sink drain above a properly vented trap?

Hi Domo,

I assume that the places you show underneath your dishwasher and kitchen cabinetry is basement or crawl space in which you have access. If so, read on; if not, never mind.

First understand there are "Dishwasher Air Gaps" which is a noun describing a physical thing you can buy such as this:

and then there is the adjective describing an air gap. For the latter, think a commercial sink in a restaurant which never has the drain connected to anything



or the contraption you have in your wall in your laundry room, in which you place your washing machine drain hose. That in itself is an air gap.




Let's think out of the box; just because your adjacent cabinet isn't a sink base now with a drain assembly in it, doesn't mean you CANNOT put a drain in that cabinet. So, let's explore one way of doing this, which is what I would do in this situation: a standpipe. Others may have other ideas.

Assuming that the cabinet to the left or right of your dishwasher is NOT a drawer base, but a cabinet base, I'd install a standpipe (think back to your washing machine drain or see photo above; the drain goes into a standpipe) in that cabinet. Choose a place about 1/2" to 3/4" from the back wall of the cabinet, close to the corner closest to your dishwasher. fabricate a tall standpipe whose top is about 22" or so off the bottom of the cabinet. Run that down to a trap directly underneath, and then over to where you have the connections now. Yes, you may have to cut and piece some PVC but that is always cheap and easy when access is readily available. Now, you have a drain in that cabinet, and you can run the dishwasher drain directly into that. Resist the temptation to completely cover the top assembly with duct tape or something--one added benefit of the standpipe method is not only is it an air gap, but it also admits air to the DWV system as needed.

Be sure that your run of PVC drain under the home to the existing system has a gentle slope so it drains properly.



Some of the dishwasher manufacturers will ASSUME that not every installation will have the conventional "right next to the sink" deal, so they do have these schematics available either deep in their installation guides or online.
Don't forget you still need that high loop off the dishwasher drain.

I don't know what code is in Canada, every code is different and some are wacko. I know that in some places, they now require both GFCI and AF (Arc Fault) circuits on dishwasher power. When I replumbed a new dishwasher recently the GFCI made sense and was cheap and easy; the Arc Fault was not so I left it out. I want to say that after owning dishwashers of a number of brands for over 40 years in a number of homes, none with AF or GFCI, I decided that the GFCI was sufficient. In North Carolina, they require you to hardware the dishwasher power to a wall switch! Want to know how many times this was accidentally turned off during a wash cycle? They also require hard-wiring (no outlet) the garbage disposal--no outlet there either. As I just bought a home in NC I can tell you I'll change this when I get to it and put in an outlet and air switch for the disposal.

FYI..."or the contraption you have in your wall in your laundry room, in which you place your washing machine drain hose. That in itself is an air gap."

That is not an "air gap". That is an "air break"

Gee, DieHard, are you the word police, a linguist or trying to help the poor guy?

801.2 Air Gap or Air Break Required.
Indirect waste piping shall discharge into the building drainage system through an air gap or air break as set forth in this code.

Whether you call it an "air break" or "air gap", it's totally and completely irrelevant in this context; it's indirect waste piping and achieves the same purpose here; in this particular case, prevention of any possible back flow from the drain system back to the dishwasher, in that most unlikely situation where it possibly could.

I merely pointed this out with photos so the poster would understand. It's not terrifically relevant what you call it, and not terrifically relevant to the schematic of a standpipe installation to solve his issue. And don't criticize this solution--I didn't invent it, but it is one suggested by dishwasher manufacturers. Not every dishwasher's optimal location for the HOMEOWNER is next to the sink. It is for the builder.

https://producthelp.fisherpaykel.co...age_Options._Determine_Which_Is_More_Suitable.

Diehard said:

How, exactly, is it tied into the sink drain line?
Is dishwasher drain hose looped, then tied into your sink drain above a properly vented trap?

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I have a sink drain with a tailpipe designed for a dishwasher. The dishwasher drain has a loop as well. As far as properly vented? That is questionable. The previous moron - err - owner put a separate trap for the disposal side and the sink side but both merge into the drain. Frequently one side siphons out the other. Due to how he buggered and glued it all up it needs quite a bit of work to be redone with a single trap.

this drawing is not per code
an air tight connection at the stand pipe is not an indirect drain nor is it an air break
what it is , is a direct connection, and that is illegal

The picture is correct it’s just the description is wrong. You are correct in that you do not want an air tight connection there, if so it would not be a standpipe anyway. The words don’t match the picture; the picture shows a stand pipe connection much like that for a washing machine—no air tight connection. The words say something else and don’t make any sense.

What I have seen on occasion is people using large amounts of duct tape to effect an air tight connection on a standpipe, and that’s not right.

PlumbGate, can’t you splice in an AAV into that s-trap configuration?

Jeff Handy said:

PlumbGate, can’t you splice in an AAV into that s-trap configuration?

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Where would I put it? There is no place to plumb it that I see. I'd like to take that entire left side out and hook the disposal drain into the tail pipe area before the trap. I should not need an AAV though right?

Also water tends to sit in my disposal until I turn it on and then water shoots out of the sink drain. If I don't have the strainer in it shoots out like 6 feet in the air.

Cut the crap out, toss it
go back with a coupling down low, and replumb the drain so that it is CLEAN looking
add a CO and put the AAV up as high as it will go
run the dishwasher hose up high then into the garbage disposal where it has an internal air break
turn the water on, check for leaks, grab a cold beer maybe 2

frodo said:

Cut the crap out, toss it
go back with a coupling down low, and replumb the drain so that it is CLEAN looking
add a CO and put the AAV up as high as it will go
run the dishwasher hose up high then into the garbage disposal where it has an internal air break
turn the water on, check for leaks, grab a cold beer maybe 2

View attachment 22857

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I would cut everything out back to the 4" large pipe if I could and do it correctly. I don't know how to re-use that pipe again though. I have never used one of those reaming tools would that work on a pipe this large? I am afraid if I get it all cut back it will leak at the reamed joint. I can't really go below the cabinet without extensive cabinet disassembly. This is a corner cabinet so I can't just take it out. Also has granite countertops on it.

yo do not have 2'' of pipe showing below that 3'' 90

frodo said:

yo do not have 2'' of pipe showing below that 3'' 90

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Ah - yes actually I do. for some reason I was thinking I needed to keep that 90. But I could cut all that out and totally start over. Do I need an AAV on here? My assumption is the plumbing is properly vented. The AAV goes after the trap, right? Just a tee coming straight up off that pipe coming through the bottom of the cabinet the top side going to the AAV?