Another garbage disposal that is too low?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by supermattthehero, Jun 28, 2011.

  1. supermattthehero

    supermattthehero New Member

    Messages:
    78
    Location:
    virginia
    Hi,

    Just had granite countertops installed today with a new undermount sink, and now it appears my garbage disposal may be too low for the drain coming out of the wall. Does it look like I need to move my "tee" in the wall lower? Currently the bottom of the disposal discharge is 13 inches above the cabinet floor.

    (BTW, I know that there is no purple primer on the PVC pipes...it was like that when I bought the house. Honest!)

    Thanks in advance.

    Attached Files:

  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,152
    Location:
    Bothell, Washington
    That's pretty typical.
    Plumbers used to plumb for 7.5" deep sinks. Many Granite counters are going with 10" undermounts making the outlet of the disposer too low. It's hard to drain a disposer when the water has no place to go.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,874
    Location:
    Cave Creek, Arizona
    The disposer water having "no place to go" is only part of the problem. Water standing in the disposer can cause corrosion, odor, and vibration when it is turned on until that water is pumped into the drain. The tee in the wall should be lowered, but it would have been MUCH easier before the countertop was installed.
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    That dip in the dishwasher drain hose may collect water and be an odor problem. Does your code allow you to NOT have an air gap???
  5. supermattthehero

    supermattthehero New Member

    Messages:
    78
    Location:
    virginia
    From Virginia Plumbing code:

    802.1.6 Domestic dishwashing machines.
    Domestic dishwashing machines shall discharge indirectly through an air gap or air break into a standpipe or waste receptor in accordance with section 802.2, or discharge into a wye-branch fitting on the tailpiece of the kitchen sink or the dishwasher connection of a food waste grinder. The waste line of a domestic dishwashing machine discharging into a kitchen sink tailpiece or food waste grinder shall connect to a deck-mounted air gap or the waste line shall rise and be securely fastened to the underside of the sink rim or counter.

    It would appear that it is sufficient to securely fasten the dishwasher discharge hose to the underside of the counter. Now, what that means exactly, I'm not certain. I am surprised, if I did need an air gap, that the granite supplier didn't drill a hole for one, seeing how he is the Angie's list #1 rated granite supplier in my area.

    I will be lowering the galvanized steel tee by using my Sawzall today, and cutting it down within the confines of a drawer cabinet. This will not be fun or easy.
  6. Jerome2877

    Jerome2877 In the Trades

    Messages:
    397
    Location:
    BC
    That galvanized pipe should be supported before cutting it. They can be pretty heavy depending how far it go's above where your cutting!
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    So your code does not require the air gap.. The best granite installer..at least around here....knows bubkus about plumbing and would never volunteer an extra hole. You have to specify exactly what you want'
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,874
    Location:
    Cave Creek, Arizona
    You would have been very angry at the granite guy if he had drilled the extra hole and then you did not need it. Water in the dishwasher hose will NOT create an odor problem because there is no way for air to circulate through it. In fact, it ALWAYS has water in the portion of it BEFORE the high loop, where it is fastened to the countertop.
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