Stand Alone Dishwasher Drain

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Old 12-04-15, 11:35 AM
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Stand Alone Dishwasher Drain

I am in the middle of a kitchen renovation and have run into a potential issue with how the dishwasher drain was piped in the past. The dishwasher drained into a standpipe below the floor the floor with a p-trap under it connecting it to the main waste pipe. It has no vent other than where the main waste line turns up the wall to vent through the roof about 6' horizontally above where the p-trap connects to the main waste line.

The kitchen is a U shape, so the drain pipe has to run through cabinets and a 90-degree turn to get to the sink...I'd rather not do this. Attached are 3 options that I came up with...1)Leave as-is and reinstall dishwasher like it was before; 2)Leave trap as-is and extend standpipe up through floor as high as possible, or 3)Completely redo piping for dishwasher drain. Thanks for any help.


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Old 12-04-15, 01:33 PM
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the drain pipe has to run through cabinets and a 90-degree turn to get to the sink...I'd rather not do this
I can't address the vent issue, although AAV's are getting more common here.

I wanted to recommend running the drain through the cabinets. I do it all the time and it can be done very neatly. I usually run the line directly under the middle shelf or lazy susan.
If you are going through a 36" corner cabinet, plus maybe one more cabinet, then into sink base, the dishwasher can pump that far no problem.
 
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Old 12-07-15, 09:51 AM
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I may connect to the sink like you recommended. The sink is a 48" corner cabinet plus about 3' away from the dishwasher. So I'm looking at about 6' or 7' of drain line to get there. Instead of going through the cabinets, would it work if I took the drain down through the floor and ran under the floor joists in the crawlspace, then back up into the sink cabinet? I would probably use CPVC through the crawlspace if I did this.
 
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Old 12-07-15, 11:32 AM
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I guess that would work.
You will need to provide a means to disconnect drain line from any piping below the floor. More trouble than it's worth IMO and not a standard installation.
 
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Old 12-07-15, 11:57 AM
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I agree with Brian that your easiest and safest way will be to go through the cabinets.

I wouldn't run the drainpipe under the floor, the washer pump will have to work harder to pump it back up, and any gunk in the pipe will collect at the low point.

Alternatively, your option 3 drawing is the right way to do it if you do want/need it's own dedicated drain. As you've drawn, it needs its own vent and the trap should be above the floor level per standard plumbing codes.
 
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Old 12-07-15, 02:24 PM
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I haven't read the entire thread but you MAY be able to use what is called a "Johnson Tee" for your dishwasher drain. They are not too common outside of my area, and your local plumbing code may not accept them, but if acceptable it is a really slick way of handing dishwasher drains.

https://www.google.com/search?q=john...utf-8&oe=utf-8
 
 

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