(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 15 of 15

Thread: Help me install a dishwasher drain below the floor...

  1. #1

    Default Help me install a dishwasher drain below the floor...

    Hi guys, Great forum, just spent an hour reading the posts on here, but I thought I would post my own dilemma...

    I have an island sink, with the dishwasher accross from it. The builder of the house put the dishwasher drain rough-in under the floor into the basement, just before the p-trap for the sink. When I installed my dishwasher, I noticed that the standard drain line for the dishwasher was not long enough to reach across, so I purchased another one to extend it and hooked the drain line into this connection. I did not high-loop the drain as I didn't have any room to do it.

    The dishwasher did not run properly, as at times water was being syphoned out. I went down in the basement and noticed that the laundry sink was nearby to where the dishwasher is installed, and to my knowledge is properly vented.

    I decided I would add a drain under the floor with a p-trap, loop the dishwasher drain line right behind, against the dishwasher, and have it go through the floor into this p-trap, and tie the p-trap off a tee that was used for venting the laundry tub. I have ran it this way, but I still cannot get the dishwasher to drain properly.

    Any help would be greatly appreciated. Would the easiest way be to run a standpipe from the laundry sink, and have it drain into there? I am very frustrated with this at the moment, and I have a feeling this drainage issue is going to reduce the life of my dishwasher as I can sometimes hear it spending a lot of time trying to drain...

    Thanks guys, really appreciate it.

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    Location
    San Diego
    Posts
    9,001

    Default

    Well, the trap for anything, cannot be under the floor. It is poor planning and design to place the dishwasher remote from the sink, and not have a proper drain plumbed to it during construction. If you had a kitchen designer involved, I would read them the riot act.

    But, you are stuck with what you have. How about a diagram or picture of the layout so we can figure out if there is a reasonable way to get this hooked up.

  3. #3
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,655

    Default Dw

    Well, from your description we cannot tell what, "the dishwasher does not drain properly" means, since that could describe several different conditions. But essentially, if there is a place for the dishwasher to drain, AND the pump is working properly, it should drain the water out of it. HOWEVER, there are many ways that the water could return afterwards if the drain is improper, and without an ACCURATE drawing or picture, we cannot diagnose it.

  4. #4

    Default

    Hi guys,
    sorry for the lack of description. When I said that the dishwasher does not drain properly, I meant that either water gets syphoned out during a wash cycle, or the dishwasher pump has a hard time pumping all the water out of it while it is draining. Here is how the original builder rough-in was, and how I had originally installed the dishwasher:



    The issue with this install was the water was occasionally getting syphoned out.

    This is the kitchen sink drain, as it comes through the floor into the basement. It almost directly across from where the dishwasher comes through, but a good 10' away. As you can see, I removed the original dishwasher bib that was left there by the builder:



    This is where the dishwasher drain hose comes through the floor and connects to the new drain that I had installed:



    That drain tees into the top of the stack that is shown to left here. As you can see, it is also tied into the laundry sink:



    Right now how the dishwasher is setup, behind it, attached to it, the dishwasher drain hose comes out of the bottom, goes up the left side of it, is bracketed onto it through one of the case screws, and comes right back down and through the floor, and into that drain I was showing you guys. With this setup, sometimes water is left in the bottom of the dishwasher, or the pump takes a very long time getting rid of the water. Is the loop too high?

    Thanks a lot guys, Please help me solve my dilemma...

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Location
    Bothell, Washington
    Posts
    14,202
    Blog Entries
    1

    Default


    It needs to look more like this.
    You need to pull a plumbing permit and let an inspector walk you though this.

  6. #6

    Default confused also

    I am currently installing a dishwasher in a similar location.

    My plan is to use the high loop method (in a cabinet adjcent to the washer before it ties into new 2" PVC) and then trap and revent the drain below the floor.

    I don't see the problem with this and am confused as to why, in other threads i've been researching, there seems to be some conceptual theory that a sink installed immediately adjacent to the dishwasher magically makes it drain properly.

    What am I missing here?

    edit: Jimbo, just reread your post. Come on now, you don't have a bath tub / shower in your house? or does it not have a trap? ("the trap for anything, cannot be under the floor"), huh?
    Last edited by rightytighty; 06-01-2009 at 12:14 PM.

  7. #7

    Default

    How long is your hose from the dishwasher to the drain?
    Got a high loop in the hose in your new configuration?
    Is that new drain 2" all the way to the vent?
    how far is the horizontal run to the vent?
    Anything draining into that vent above where the dishwasher drain ties in?
    Last edited by rightytighty; 06-01-2009 at 12:19 PM.

  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Location
    Bothell, Washington
    Posts
    14,202
    Blog Entries
    1

    Default

    Laymen may not understand plumbing codes,
    For instance, there are limits as to how long a tail piece can be.
    Too long, and they self siphon the trap.

    That is why sinks, washers and dishwashers don't have traps under the floor. Dooh!

    It's not like all this stuff hasn't been thought of before.

    Get a permit, and argue with your plumbing inspector.

    Don't get on a DIY board and assume that the plumbers are going to praise hack plumbing.

  9. #9

    Default

    no assumptions, just questions. Afterall, I'm hear BEFORE I install this thing, because I'm trying to learn from you guys. And, yes, I see that this has been deliberated often here. Guess i just wanted to ask for myself.

    Thanks Terry. No offense intended.

  10. #10
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Location
    Bothell, Washington
    Posts
    14,202
    Blog Entries
    1

    Default

    As plumbers, we try to ask first too.

    On some non-standard jobs, we will meet with the plumbing inspector first, before the work even starts, getting all of our ducks in a line, and finding out what it will take to please the inspector.

    A lot of time is saved that way, and feelings.
    Not that we're going to admit that out loud though.

  11. #11
    DIY Senior Member gardner's Avatar
    Join Date
    Apr 2007
    Location
    Ontario
    Posts
    217

    Default

    In your diagram, the DW drains into the sink trap. In your pictures the sink trap (1st pic) and the trap the DW runs into are different. One's tight to the steel duct and the other's more than a foot away.

    In my non-professional opinion, you are missing two critical elements here -- an air gap and a high loop.

    You may be able to get a workable air gap by having a stand pipe come up through the floor into your cabinetry, then having the drain hose feed into this, but so that it is also open to the atmosphere. This is how I did mine, where the pre-existing plumbing had a trap for the DW under the floor. Alternatively, and probably simpler you can get a commercial air gap fixture that installs into the counter top.

    You have to have the drain looped up above the top of the fixture at some point. Mine had that part of the drain path built into the DW itself, with the drain hose cable tied to the back of the unit such that the first free point was right at the top. If you use a counter-top installed air-gap, the high point will be that air-gap fixture.

    I have seen a couple of sinks with traps under the floor and my understanding is that they are bad news. Where are you located? I would be surprised if placing sink traps below the floor passed inspection, but that probably depends where and when it was built.

  12. #12

    Default

    Thanks for all the replies. I am in Brampton, Ontario, Canada, the house is 2 yrs old.

    The first diagram is how I had it installed when I first moved into the house. This did not work, because water was symphoning out of it. It is currently attached to the second run, which is shown in the pictures.

    Right now, my high loop is right behind my dishwasher, attached via strapping to the unit. It goes up, to just about the top of the dishwasher and comes right back down. With this setup, it seems like the dishwasher has a hard time trying to pump all the water out of it, and sometimes water remains inside after draining.

  13. #13
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    Location
    San Diego
    Posts
    9,001

    Default

    Quote Originally Posted by erratic View Post
    . I am in Brampton, Ontario, Canada, the house is 2 yrs old.

    .

    Not that you should assume different, but that little tidbit about being in Canada could have been shared earlier. Almost everyone on here is in the US, so we don't know your codes, but I have heard they are strict>

  14. #14
    DIY Junior Member tbull11's Avatar
    Join Date
    Aug 2011
    Location
    OH
    Posts
    1

    Default

    Terry-
    I am installing a new dishwasher in a completely new location (12 feet from sink) with no cabinets to run drain hose behind (or through) to connect to the sink drain. The basement below is a "utility" basement that will NEVER be finished. Can I just run the drain line (from above) to the utility sink below? The utility sink in the basement is properly vented and is connected to the main sewer line. This is no different than letting my washing machine drain into the utility sink? Thanks.

  15. #15
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,655

    Default

    Running a hose upwards and then down below the level of the dishwasher creates a siphon, and a siphon, whether being used to get gas out of an automobile or water from a dishwasher WILL suck ALL the water out, and could also occur when you do NOT want it to. When connected to a sink, the connection point is ALWAYS higher than the water level in the DW, so it CANNOT siphon it.
    Licensed residential and commercial plumber

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •