How to Install a Garbage Disposer—Part 3


Part Three: Prepare New Disposer—Insure New Unit Fits & Install Plug-in Electric Cord


Included in this video: Insuring new unit will fit and installing seperately purchased plug-in electrical cord on new garbage disposer (it's harder than it sounds if you are new at it… :)  

NOT IN VIDEO: How to measure and compare disposer outlet height and drain height to insure new disposer will drain properly

Video Transcript Outline and Additional Instructions for Part 3–Prepare new disposer or “It’s always something”

Ok, now you have the old disposer completely out. In my experience, here is how this usually goes:

• Carefully compare the new unit, included parts, and extra items you may have bought to the old ones. (details below)
• Go to the store. :) Unless you have a variety of miscellaneous plumbing fittings laying around the garage, expect you will have to take one last run for some little piece you didn’t know you needed. If you have everything, it’s probably a good day to buy a lottery ticket!

1. Compare new and old units

    a.  First measure the distance from the top of the unit to the center of outlet on both units.

DIY Tech Tip

Tech Tip: Place a small level across the top of the disposer and measure from the bottom of it to the center of the outlet. This is the easiest way to get an accurate measurement.

    b.  If they are the same or the distance is shorter on the new unit (and you had no problems with the old unit draining) you are good to go. Go to step 2.


    c.  If they are significantly different (more than ½” or so,) you need to make sure that the new unit will drain before moving forward.  Basically the outlet of the disposer needs to be higher than the drain opening. Water flows downhill so you need to have a slope or it will just sit in the pipe.  I’ll explain how to do this, but it sounds more complicated than it is. You just need to figure out how high the outlet will be at the beginning of the horizontal pipe and compare that to the height of the drain opening. If it is least ½” higher, you will be ok. To do this:

How to measure drain height diagram

(1)  Measure the height of the drain opening (to center) from the cabinet “floor”.

(2) Now measure the distance from the cabinet “floor” to the bottom of the sink.

(3)  Set your new disposer upright with the small level across the top

(4)  Loosely connect the two pieces of your P-trap so it is now a P shape

(5)  Now take U-bend part of your P-trap and hold it so the TOP of U-bend (higher side that will connect to disposer) is just below the BOTTOM of the outlet. Basically you are mimicking the highest possible connection.

(6)  Measure the distance from the top of disposer (bottom of level) to the center of the horizontal pipe on the P-trap.  

(7) This is the highest possible distance of the outlet from the bottom of the sink.

(8) Subtract your outlet distance from the total distance to bottom of sink,  and now you have the distance from the floor,

(9) Compare the outlet height and drain height. Outlet should be at least ½” higher. If it is not, you will need to change the drain opening before moving on. That is not covered here, Check my site for other resources.

    d.  Look at your P-trap carefully–hold the pieces in place if needed, and make sure you will be able to connect everything (will it reach? are the sizes the same? etc.) If not, go to the store :)


2.  Connect Plug-in electrical cord. (If using hard wired whip, skip ahead to Part 4 (Not in video–check written instructions on page))
    a.  Flip disposer upside down and remove electrical recess cover by loosening screw and removing.
    b.  Feed wiring through electrical input hole into electical recess.
    c. Seat rubber strain relief (stopper-type plug near disposer end of cord) in the electrical input hole.  This is easier said than done, as I discovered. To get it seated:
             (1)  Heat strain relief with a hair dryer until it is significantly softer and more pliable. This takes a while, and the strain relief plug will be quite hot to the touch.
             (2)  Now push down on one side until you have at least one small part of the plug seated inside the electrical hole.
 DIY Tech TipTech Tip:  you can put the flat side of channel locks onto the top of the stopper and push on that to get more oomph.
              (3)  Now take a flat-bladed (straight) screwdriver and starting as close to the seated part as possible, push on the stopper, near the middle “slot” designed to seat in the hole, both inward (toward the center of the hole) and downward at the same time and work that small portion down until it seats.
  DIY Tech TipTech Tip: : If the stopper has cooled and begun to harden, heat it up again before continuing. It is much easier when the stopper is flexible.
               (4) Continue working around the stoper in this manner until it is completely seated.  Once it is in, it should actually spin easily in place.

Next: Part 4—Connect eletrical wiring to new disposer.


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