Can I drain dishwasher into horizontal pipe?


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Old 01-27-18, 09:13 AM
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Can I drain dishwasher into horizontal pipe?

We are installing a dishwasher, and the drain pipes are really pretty tight under the sink. The sink is a farmhouse sink and sits very low. As in the picture, there is really no room to add the pipe with the side connection for the dishwasher drain. Would it be ok if I put it in the horizontal pipe with the dishwasher drain connector pointing up vertically?
Thanks Dave

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Old 01-27-18, 09:17 AM
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Generally you want to use a dishwasher tailpiece directly under the sink.

https://www.keeneymfg.com/installati...67-en-PP66-14B
 
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Old 01-27-18, 10:27 AM
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Looks to me you have enough room to drop the trap and add the tail piece with dishwasher adapter as shown in X's reply above. You'll need to add an extra piece to the lower section of trap.

PS...I don't think dumping the dishwasher drain into the horizontal will work. It may back up into the sink.
 
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Old 01-27-18, 11:09 AM
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Thanks guys. Will do it the way you recommend.
 
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Old 01-27-18, 11:16 AM
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You don't have much room at all. To gain a little height you can swap out the sink basket strainer. Your existing strainer is unusually deep and a new strainer will give you at least another inch or two.

Here's a link to an ABS dishwasher Wye adapter, this is shorter than a slip tube branch tailpiece and it looks like it will work:
https://www.plumbingplanet.net/produ...asher-adapter/

Cut the vertical pipe coming up from the trap, leaving about a 3/4" stub for gluing on the new piece.
You also want to make sure that the branch part of the adapter is installed above the bottom of the horizontal pipe that goes into the wall.
Make the branch as high as possible to prevent backflow.

I doubt if you will find this adapter in a store, you will probably need to order it.
 
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Old 01-29-18, 07:58 AM
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Sorry for the dumb question, but after I add the wye, the trap will be lower. How will I get the pipe up higher to connect to the horizontal pipe?
 
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Old 01-29-18, 01:13 PM
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You cannot make the trap lower with some kind of adapter, water doesn't travel uphill. You need to fit the wye between the trap and the bottom of the strainer basket.
First install a more shallow basket strainer, yours is way too deep and changing it will gain you height.
After swapping out the basket, cut above the trap (yellow line) leaving exactly 3/4" and glue the Wye on.
Above the Wye, glue in a male trap adapter, 1-1/2":
https://www.homedepot.com/p/1-1-2-in...D112/100344703

Once you have the Wye and trap adapter installed and glued, connect the Wye to the strainer using a short tailpiece and a tailpiece washer, The new basket strainer will come with a tailpiece washer.
Purchase a PVC 1-1/2" x 6" tailpiece and cut it down to a short length.
This is not the easiest job for someone with no experience but it can be done.
 
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Old 02-07-18, 07:41 AM
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Thanks again. Iím going to tackle it later his weekend. Iíve done a fair amount of minor plumbing. One last question...with the side leg on the wye, what part needs to be above the bottom of the horizontal pipe? The top of it, or the lower part where it meets the 1.5 inch part? I also plan to run the drain hose from the dishwasher in a high loop under sink
 
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Old 02-07-18, 09:31 AM
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Try to get the branch part of the Wye above the bottom of the horizontal pipe.
The branch is the arm where the drain hose connects.
When I said cut exactly 3/4" above the trap, that was meant to say at least 3/4". Cut it a little higher if you have room.
It looks like you will have room for the Wye and short tailpiece if you change out the basket strainer.
 
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Old 02-12-18, 05:11 AM
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Just wanted to post an update. tackled it on Saturday. I was able to get the branch of the wye high enough. I also looped the drain hose up high. I have a very tiny drip from the tailpiece where it attaches to the strainer. I will put some pipe dope on the treads and washer. Thanks again for all your help.
 
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Old 02-12-18, 06:30 AM
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I have a very tiny drip from the tailpiece where it attaches to the strainer
Ensure you use a tailpiece washer. Also try tightening the tailpiece to the basket before you tighten the trap nut below.
The tailpiece needs to be perfectly straight.
 
 

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