Dishwasher drain directly into waste line

[Terry]

If you local code allows a high loop on the dish washer drain, then it can connect to a p-trap and standpipe, to a disposer, or to a outlet tee below your sink.
If you are in a locality that "requires" and air gap, then either a counter mounted air gap, or a Johnson tee will work.

Since you are in New Jersey, you most likely will not be required to have the air gap.

The standpipe would have a 1-1/2" reduced town to 3/4" FIP with a 3/4" MIP x 3/4" barbed fitting for the dishwasher hose.

 

[Violin]

I don't like the standpipe.

It looks like I'll make my own Johnson Tee out of PVC parts.

It will be on an interior wall about 12" from the exterior wall and I plan to run a length of PVC to the exterior vent.

Any problems with that idea?

Should it slope down 1/4" toward the exterior?

Thanks.

 

[Sponsor]

 

[Inspektor Ludwig]

The pumped discharge does not need to be sloped but read your manufacturer's installation instructions on the length and height of the pumped waste. Some manufacturers will not warranty their product if you use a "Johnson Tee" such as Meile (I've had many battles over that one) and others will have a maximum allowable pumped length, if you exceed that length then it voids the warranty. .just a heads up.

 

[Violin]

Good tip - thanks.

 

[Violin]

One last question:

The photo at the beginning of the thread shows copper up to the Johnson Tee whereas I've also seen photos with PVC, like this:

Is there any good reason not to use the PVC (it would make it much easier to get the drain exactly where I want it)?

 

[Geniescience]

ok to use PVC. Never required to use copper, in any drain.

 

[BrandonT]

One last question:

The photo at the beginning of the thread shows copper up to the Johnson Tee whereas I've also seen photos with PVC, like this:

Is there any good reason not to use the PVC (it would make it much easier to get the drain exactly where I want it)?

I know it's a long shot since this post is old, but any chance you have pictures of how you made this work? How has it been since installation? Have a similar setup where the dishwasher is on anew adjacent wall to the sink and separated by a corner cabinet... already taken the walls down to the studs, so I'd like to make sure we do it right!

 

[Terry]

In the Seattle area, the Johnson was often used. It works very well, just like the picture on your post.
It does need the vent through the roof, and the 3/4" cap either turned to the outside, or the inside gets a 1/4" hole drilled in it, or the cover with holes.

 

[Steve.Richfield]

SewerRatz,
I have a home with TWO dishwasher drains just like in your photo, one above the other on different floors. Now, after decades of service, it appears that the J trap on the upper drain has silted up and clogged (the pipe above the trap is full of water), leaving no obvious way of cleaning it out. It has a 3/4” cleanout like in your picture, but I don’t know what I might put into it to clean out a 1-1/2” trap that is a yard below it.

I have “temporarily” rerouted the dishwasher to the sink until some route to repair has been identified.

Any suggestions how I might clean out such a thing?

Thanks.
Steve Richfield
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I never met a plumbing inspecter that allowed the dishwasher to drain to a lower level. But he has allowd the dishwasher to be installed as pictured.