This is an updated version of the product training course introduced by SUPPLY HOUSE TIMES in 1979, authored by Don Arnold.

It's definition time again. Alternately called by such names as “disposer,” “garbage disposer,” “garbage grinder,” “disposall,” and “food waste disposer,” the product we're discussing here is installed in the drain outlet of the kitchen sink for the purpose of grinding up garbage and flushing it down the drain. (Technically, the term “Disposall,” a trademark of the General Electric Co., is not intended as a generic identification of all such products.) The terms most commonly used by the companies making these products are “garbage disposer” and “food waste disposer.” From the standpoint of relating the name to its function, the latter term is probably one of the better choices.

To some people, the word “garbage” can mean just about anything you would otherwise toss in the garbage can, including paper, glass, string, metal and plastic objects - materials not meant to go into a disposer. While a good disposer can do an amazing job on most food wastes, these other materials can do an “amazing job” on a disposer.

How They Work

It's surprising how many industry people really don't comprehend the workings of a disposer. In reality, what happens down in that “dark hole” is really not that mysterious. When garbage is pushed down into the grind chamber, it falls onto a rapidly spinning turntable that flings it by centrifugal force against a series of cutting teeth around the perimeter. Spinning the garbage against these teeth (technically called the grind ring or shredder ring) causes a grating action that reduces the waste into particles about the size of rice grains. The ground particles then pass between the grind ring teeth to the chamber below, where they are flushed (by water running through the disposer during use) through the disposer outlet and into the drain system. This flushing is important to prevent a buildup of residue in the disposer's lower chamber, as well as in the smaller diameter portions of the connecting drain line. That's really all there is to the mechanical concept of a disposer, and almost every disposer made today works on the same basic principle. When you talk about product features, you're really dealing with refinements and extras added to this basic concept - which brings us to the next part of our discussion.

Motor Sizing

In terms of quality, one of the most fundamental criteria concerns the power of the motor provided. As you might expect, low-cost disposers are equipped with the smallest motors; high-grade types use the largest. The most common motor sizes in terms of horsepower are the 1/3 and 1/2 types today, though most manufacturers offer top-of-the-line 3/4 and 1 hp models. (Disposers equipped with the smallest motors are sometimes called “builder models,” since these are commonly used in tract housing and apartment construction.) It is important to understand that increased horsepower provides an advantage in terms of increased torque, not necessarily related to speed. The key benefit of a more powerful motor is that it is less prone to laboring and jamming.

Type Of Feed

There are two basic methods of activating a disposer - batch feed and continuous feed. By batch feed, we mean that a load of garbage is inserted into the grind chamber, and the motor is started by placing the stopper down into the mouth of the drain flange. The continuous feed variety is far more common, and is pretty much the standard today. With this type of disposer, you turn the unit on by flipping a remote wall switch before you begin inserting the garbage. Rather than periodically feeding the garbage in batches, you just keep inserting small quantities until it's all gone. From the standpoint of installation, of course, this type is a bit more involved since in-wall wiring must be provided to a switch location. (As an alternative to the wall switch, some manufacturers now offer an “air switch” mounted into the faucet ledge of the sink. This is essentially a pneumatic relay that transfers a column of air to an electrical switch below.)

Turntables & Impellers

The component connected directly to the motor shaft is called the turntable. These are the things to be aware of in this area:

1) The material makeup of the parts. Galvanized steel and stainless steel are the most common materials in use, with the latter deemed the higher quality choice because it is more resistant to corrosion and acid attack (typically, it is used on better models).

2) Impellers on a turntable are the lugs located near the edge which assist in keeping the garbage spinning against the grind ring. Without them, there would be a tendency for the garbage to “float” while the turntable continued to spin below the mass. Initially, these were stationary, functionally integral to the turntable. Following this came the development of the current type in which the impellers swivel on bolts or rivets at the turntable's edge. The advantage of this approach is that the impellers, if they are about to enter a jam condition, automatically back off and thus avert the jam.

Grind Ring

Like the turntable, the grind ring used in most disposers today is made of either high carbon or stainless steel.

Sound Dampening

One of the features offered by most manufacturers on better grade models is the sound insulating jacket designed to lessen noise levels. Actually, the means of suspending the disposer from the sink makes an equally important contribution to quiet operation. There needs to be a means of insulating against vibrations caused by a disposer, to prevent amplification by the sink (thin gauge sinks, especially, tend to resonate noticeably unless such provision is made). While these measures help to some degree, a good portion of the operating noise of a disposer simply comes up through the opening in the sink.

Automatic Reversing

In addition to the power rating, there is one other basic difference in disposer motors today, having to do with the motor's direction. In other words, while some motors turn clockwise only, automatic reversing models alternately turn clockwise and counterclockwise with each flip of the switch. This feature extends the life of the grind components. If you picture each of the teeth in the grind ring as having two sides or “blade edges,” you can see how spinning the garbage in only one direction will effectively use only half of the cutting surfaces. In time, these surfaces will wear, while leaving the others unused. By alternating the direction of operation with each throw of the switch, however, you get equal use from both sets of cutting surfaces.

Overload Protector-Reset Button

Most current disposers are equipped with an overload protector device to break the electrical circuit when the motor overheats (which would most typically occur in a jam condition or when the disposer is overloaded with garbage, causing the motor to labor). When the overload protector kicks out, a cooling period (typically a few minutes) is required before reactivation is possible.


To understand the placement of the disposer, it sometimes helps to view it as a part of the regular drainage system connected to the sink, taking the place of the strainer and tailpiece normally in this position. From there, the elbow outlet of the disposer is connected to a 1-1/2-inch trap, as would be the case with any sink drain system. The other drain connection often made on a disposer is an incoming type, connecting the unit with the drain hose of a dishwasher. The dishwasher inlet on a disposer takes the form of a nipple, over which the dishwasher hose is clamped. Before making such a connection, however, there is a knockout plug inside the nipple that must be removed to open the passageway. (For non-dishwasher installations, this plug is just left in place.) The installation steps involving the attachment of the drain elbow and the removal of the dishwasher knockout are best made prior to mounting the unit, since access is more convenient before mounting the disposer to the sink. The final installation step involves connection to the electrical provision nearby. Here again, in many cases, the wiring to the disposer itself is made prior to the mounting procedure, since access to the terminals is much easier beforehand. After the disposer mounting and drain connections are completed, the other end of the electrical cable or conduit is connected to the line serving the installation.


Swivel impellers or not, there are few manufacturers who would make a claim for absolutely jam-free service. There are various remedy approaches, depending on the make of disposer. The freeing of the obstruction can range from the use of a special tool (large Allen wrench) inserted into an opening on the bottom, or something high-tech like sticking a broomstick down onto the turntable to force it in the other direction (away from the jam). Once the obstruction has been dislodged and removed, it's a good idea to spin the turntable by hand to be sure it turns freely. If it does, turn the power back on, to see if the disposer operates properly. If not, it could be that the overload protector has “kicked out.” Once a few minutes have passed since the motor stopped, the power can be reactivated by pressing the reset button. <<


The College of Product Knowledge ran in Supply House Times for three years and resulted in a reprint manual that sold for many years to follow, totaling thousands of copies. It became something of an industry classic. Much of the original training material is still applicable to the products sold today - but there is also much in the wholesalers' product mix that is new since then. The purpose of this updated series is to look at what has come along since the first edition.