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Thread: install garbage disposal in double sink

  1. #1
    DIY Junior Member homey6660's Avatar
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    Default install garbage disposal in double sink

    I am installing a garbage disposal (1/2 hp, Insinkerator Badger 5) under a double-sink. I would like some help determining how to plumb the sinks/dispoal (no dishwasher). I have a picture if someone offers to help off-line.

    Right now, the discharge hole/port from the disposal would line up with the horizontal pipe that leads to a t-coupling (conntecting the drains from the two sinks), then down to a p trap and up to the waste pipe. Ideally, I'd be able to just cut that horizontal pipe (meaning, cut a new horizontal pipe) and connect it without making any vertical changes in the piping (I've probalby lost you by now). But, the instructions say I should have separate drain traps for each side. And, the disposal comes with a "discharge tube" that comes out and goes 90 degrees south. If I had to put on that discharge tube, it means a lot more re-configuration, as I'd have to either have those separate traps leading to the waste pipe. And, I wouldn't even know how to set that up.

    Anyhow, that's enough rambline b/c I'll only confuse us more. Is anyone aware of some basic double sink garbage disposal installation instructions? Can anyone help out with my specific situation? Drawings?

    Your assistance is much appreciated.

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Default


    You can use two p-traps, or pick up a "disposer kit" with a baffle tee that goes straight out from the disposal.

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    DIY Junior Member homey6660's Avatar
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    Default f/up

    I saw that diagram and thought it was helpful. The problem is that the disposal I have says that I should use separate drain traps for both sides. Why would you think that is required?

    Also, I'm not sure what I'd do with that discharge hole -- not sure if the discharge tube they provide is specially fitted/seated such that the horizontal piping won't fit there. I have a link to the instructions here:

    http://www.insinkerator.com/pdf/US_ICU1.pdf

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    Forum Admin, Expert Plumber Terry's Avatar
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    Where does it say that on the pdf?

    I see where it mentions that they prefer the turned down pipe, but that you can use a straight pipe out of the disposal. 11-2

    Insinkerator is mainly what I install.
    Many sinks have two bowls, it's not uncommon.

    Installing the Evolution in the Seattle area.

    Last edited by Terry; 02-27-2014 at 09:12 PM.

  5. #5
    DIY Junior Member homey6660's Avatar
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    Default trouble with "flange" and "drain" (if I have the terms correct)

    Installing a garbage disposal. Got all the pipes off (I'm replacing corroded pipes down there, too). Problem is, the "drain" (basically, the first part that connects to the pvc below the sink) won't separate from the "flange" (the part that lays on top of the sink. Not sure if I have the terminology correct. I know some are screw mounted, but this one is threaded and just completely stuck. The flange and the drain turn as one.

    Any advice?

  6. #6
    DIY Member King3244's Avatar
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    Default

    Pair of plyers upside down, stick handles down into drain from sink side to hold that part, then turn pvc/abs part underneath.

  7. #7
    DIY Junior Member homey6660's Avatar
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    Default done

    a lot easier than expected. Thanks to those who responded.

    Much appreciated!!

  8. #8
    DIY Junior Member Derek's Avatar
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    Question InSinkErator's preference for 2 drain traps

    The InSinkErator instructions call for 2 traps on item 4, step 11, middle of page 5 in the PDF. ("If you have a double sink, use separate drain traps for both sides.") This is true for both the one-bolt and two-bolt discharge tube installation.

    I'm also told (by a How-To brochure on disposers I picked up a Lowe's yesterday) that many local communities require two drain traps by code.

    I am about to replace my old disposer with a new one and I can't imagine adding a second trap. Major hassle since cutting in my kitchen wall would be required, rather than a quick 30 minute swap.

    Any thoughts on why InSinkErator and some local codes suggest it?

    Thanks much,
    Derek (plumbing Newbie who did a toilet last weekend)


    Quote Originally Posted by Terry
    Where does it say that on the pdf?

    I see where it mentions that they prefer the turned down pipe, but that you can use a straight pipe out of the disposal. 11-2

    Insinkerator is mainly what I install.
    Many sinks have two bowls, it's not uncommon.

  9. #9
    DIY Junior Member wyaifg's Avatar
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    Default InSinkErator's preference for 2 drain traps

    The PDF states to use 2 traps in step #11 item #4

  10. #10
    Homeowner geniescience's Avatar
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    Default makes sense to me...

    FWIW, my thinking on this subject. Two traps isolate everything. Isolating the two is a bit more hygienic, sanitary. No loss except a bit more time installing.

    Isolates noise too. Do disposers make noise on the drain side? Does it come up through the other sink's drain hole? Is this a problem for anyone?

    I know my 25 year old dishwasher makes a ton of noise, and I would love to have two traps, but for a dishwasher that is hard to arrange since it needs air too, so I would have to make a tall standpipe for it, if I kept it (which I won't). I have been saying "I don't get it" for years, since I believe lowering appliance noise levels is a prime objective in quality installations.

    Since I'm planning a new kitchen, I'd like to figure it out. Isn't noise a concern?

    david

  11. #11
    Forum Admin, Expert Plumber Terry's Avatar
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    Plumbing codes don't allow two traps on one trap arm.
    To have two traps, you would need two trap arms, each one properly vented.
    I don't know of very many sinks that have been plumbed that way.
    Most only have a single trap arm roughed in.
    A cross fitting in the wall would work, if the waste and vent were vertical.
    If you has a trap arm coming from the side, that you can't add the second trap.
    Last edited by Terry; 03-20-2007 at 10:08 AM.

  12. #12
    Homeowner geniescience's Avatar
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    Default two arms = reduced noise?

    i know the second trap can't go after the first one, and that probably explains why almost nobody ever installs two trap arms.

    so the dumb question is whether or not there IS a gain in doing it, even if the gain is only in terms of reducing noise.

    david

  13. #13
    Jack of all trades, Master of none KULTULZ's Avatar
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    Question

    Quote Originally Posted by Terry View Post

    Plumbing codes don't allow two traps on one trap arm.

    To have two traps, you would need two trap arms, each one properly vented.
    Terry,

    Would the below shown installation be to code?



    Source- http://www.nettally.com/palmk/GDplumbing.html
    Jack of All Trades...

    ...Master of None...

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Default disposer

    IF it says you need two traps, then the instructions were written by some engineer who had absolutely no idea about how to do it. The standard disposer, (not Disposal®), continuous waste is all you need.

  15. #15
    Jack of all trades, Master of none KULTULZ's Avatar
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    Quote Originally Posted by hj View Post

    IF it says you need two traps, then the instructions were written by some engineer who had absolutely no idea about how to do it. The standard disposer, (not Disposal®), continuous waste is all you need.
    What he is trying to overcome (I believe) is the restriction in the outlet tee.



    If one was to not use the trap @ the disposal and tee the discharge in above the other sink trap with a tee with no baffle (and 45 degree offset so as not to introduce flow into the second bowl), would this be OK? Or if one installed the trap w/o baffle @ the disposal and tee'd the second bowl into (above) that trap, would it muster?

    No dishwasher on application, but would one make a difference?

    Just trying to think of a clean way to plumb undersink to allow maximum storage space. What do you think?

    THANX!
    Jack of All Trades...

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