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bitsdoo 08-20-2010 09:37 AM

Dishwasher install...with a twist ;)
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Alright, here goes. First things first I did a search and could not find my situation so I'm starting a new thread. Doing a kitchen reno and in that replaced the dishwasher (herein DW). To make things more accessible incase there is trouble down the road I want to change the plumbing. The old DW plumbing was typical, drain going to the sink plumbing and tied in with a DW tee. DW supply also came off the sink plumbing.

Where the DW will sit is directly above my furnace room, and the point of entry of all water and the main drain/stack. I want to plumb the supply from the basement (no problem here) and tie the DW drain in to the basement as well. I've included a diagram (which is attached) of what I want to do. I think I've included all pertinant info, if you need anything else just let me know. The house is a 4 level sidesplit, with the kitchen being directly above the lowest/basment floor. Obviously there is more plumbing but it is irrelevant (IMHO).

Please provide feedback on this install, am I up to code? Do we see any issues with the plumbing and if so what do I need to change.The new plumbing is circled.

Thanks in advance for all your help.

jc60618 08-20-2010 08:25 PM

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The trap closer to stack is not allowed by most codes its considered a running trap and its not vented. With that trap there, you will be double trapping the kitchen sink and cause it do drain slow. Another issue you might have is if you have a clog on the suspended line you might have trouble going thru the P trap and down the line when rodding. Finally the tail piece (drop pipe going into p trap) must be less that 24". Below is how we usually pipe kitchens with a DW.

bitsdoo 08-22-2010 10:54 AM

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jc60618, thanks for the reply. My only problem is I can't get to the vent that easy as it is in the wall behind the cabinets. Drop pipe will be less than 24", why does it have to be less than 24" long?

I've revised my drawing to move the trap to the DW take off, thus removing the existing running trap. I don't see any issues with doing it the way I have it, anyone see any issues with this install?


the_man 08-22-2010 12:46 PM

In my code you cannot drain a fixture into a trap not on the same floor. Laundry drain trap must be on the same floor, and condensate drains cannot be in a crawlspace. You would have to extend the drain into the space w/ the dw and properly vent it thru the roof

jc60618 08-22-2010 01:08 PM

You are now creating an s-trap and the trap will siphon itself out.

TheEplumber 08-22-2010 02:49 PM

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I'm curious, why not plumb it back to the sink?

the_man 08-22-2010 02:53 PM


Originally Posted by TheEplumber (Post 489541)
I'm curious, why not plumb it back to the sink?

I agree, but the sink plumbing doesn't look right either, i'm really hoping the trap isn't downstairs for that too

bitsdoo 08-22-2010 03:50 PM

Thanks for the help folks.

The sink trap is just below the floor (literally 2" under the floor in the joists). Its right at the connection to the vent. I can see it from the basement in the furnace room up in the ceiling.

I wanted to avoid running the drain under the cabinets because I'm putting a marble tile counter top on and once it goes on I can't take it off. Also the DW drain hose will have a connection as the distance to the DW from the sink is approx. 8 feet, I'm conerned about having this connection buried behind the new cabinet install, if it starts to leak I'm screwed.:( This is why I wanted to do it in the basement furnace room where I can get to everything easily if there was ever a problem.

Bottom line is can I avoid having to put in another vent if I run the DW plumbing as I've described. Otherwise, I'll plumb to the sink and hope all the connections don't cause me grief down the road.

The drain hose that came with the DW is shotty at best, is there anything I can do to "upgrade it". Maybe just use a long length of 1" rubber hose and tie in at the DW.

Thanks for all your help folks.


the_man 08-22-2010 03:57 PM

Yea you can buy 5/8 or 7/8 hose at the hardware store by the foot. It'll be a bit expensive, but you don't want joints in it... that's what will generally leak. You can drill holes in the very back of the cabinets to run the lines, keeps them out of the way but fairly easy to get to if you need to

Jacques 08-25-2010 06:37 AM

most installers do what THE MAN said, run fill and drain through through bottom drawer of cab at rear and make your loop under sink. don't run at top ..don't buy cheap drain hose-kinks easily and causes many problems after awhile of use...some d/w have a formed curve in their drain hose off pump-if yours does, you'll be better off just adding an approved extension to the end of that hose [avail at local appl parts distrb']..remember- this unit may have to be pulled for service so you don't want a lot of drama if that happens-$$$.

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