Selecting an Under-Sink Disposal

Many people have under-sink disposals in their kitchens to get rid of food waste in a quick, easy, and sanitary manner. Disposals are often added or replaced with the introduction/replacement of a dishwasher. They consist of a motor that drives a disk that has attached to it offset blades called “grinding elements.” They reside inside a chamber called the “grinding chamber.” These small appliances, which remain hidden almost all their lives, have a wide variety of features and materials that affect power, disintegration, durability, ease-of-use, noise, and price. These six factors will determine which disposal is the best choice for you.
under-sink disposal


Disposals will have motors that range from 1/2 to 1 HP. In general, the greater the power generated, the easier the disposal will be able to handle hard and stringy foods, like bones and celery. Most will fall in the 3/4 HP range, which is plenty of power for the vast majority of people. With 1 HP, there is little the disposal won’t be able to handle.
In fact, when Ask This Old House’s Richard Trethewey toured the Emerson disposal factory (Emerson is the maker of most disposals sold in America, including the Badger, InSinkErator, and Kenmore brands), he saw their testing facility in which disposals were fed cow bones, wood blocks, and various fruits and vegetables. The greater the power of the disposal, the less it has to work to get the job done, and the smoother the operation when fed this assorted mix of materials.
Generally, 1/2 HP will not be worthwhile, as it is only going to be able to handle softer, less stringy food waste. 1/2 HP models are usually purchased by housing developers and home sellers. They are not often purchased for personal use.


More powerful disposals will usually churn food solids into finer particles than less powerful disposals. For instance, a 1/2 HP model is going to produce little chunks of carrots, while a 3/4 HP model will produce something more like slightly chunky baby food, and a 1 HP model will produce a fine paste. The finer the particles, the easier it washes down the drain, and the fewer build-ups you’ll have in your pipes. For this reason, 3/4 HP is the usual starting point for customers looking for a disposal for their own kitchens.


There are several combinations of materials inside a disposal:
  • Plastic grinding chamber with galvanized steel grinding elements
  • Plastic grinding chamber with stainless steel grinding elements
  • Stainless steel grinding chamber with stainless steel grinding elements
Plastic with galvanized steel is the least durable. Plastic scratches and cracks, and galvanized steel corrodes. This is why models (1/2 HP) with these materials have 1 year warranties. The manufacturer knows this is not a machine that is designed for long-term use, and the buyer should notice that the price is considerably lower than all the rest. Plastic and galvanized steel are cheap materials, which makes the price lower, and makes it less durable.
Plastic with stainless is a moderate step up. The grinding elements, which are the parts that do the lion’s share of the work inside the grinding chamber, are going to be durable, but the chamber itself is still plastic, and still vulnerable to scratching and cracking. This is a decent combination of materials, and is found in entry-level 3/4 HP models.
Stainless with stainless is the most durable. The chamber and elements are both made of stainless steel, so they are not vulnerable to rust or corrosion. These materials should last, in almost all cases, well beyond the manufacturer’s warranty period (usually 7-10 years for these models). Most 3/4 HP and all 1 HP models will be made with these materials, and are highly recommended for their durability.


There are two basic types of disposal: continuous-feed and batch-feed. Continuous-feed disposals can have food waste put into them at any time while it’s running (as long as you’re also running water). You just turn it on, throw down some food, and turn it off when it’s done.
Batch-feed, on the other hand, requires you to fill the disposal, then put on a special cap over the opening that allows the disposal to be turned on. Some people like the continuous models for their wide range of prices and features. Others like batch because they have safety concerns. Neither does a better job, they’re just different. However, batch-feed disposals do not have many different models available, and they usually have to be ordered, as they are not as popular as continuous-feed models.
Some continuous-feed models will have a feature called “auto-reversing.” This is usually found in 1 HP models, and will eliminate the need to use the disposal wrench when an especially hard piece of food causes a jam. Rather than the disposal shutting down, it will simply reverse the rotation of the grinding elements to dislodge the jam, then resume grinding. This feature adds to the longevity of the disposal by reducing excessive motor wear, and keeps you from having to get under the sink to wiggle that offset hex wrench in the bottom of the disposal to get it going again.


The most basic disposals will have no sound insulation. They will be a little noisy when running without food, but will be very noisy when running with food. As you progress up the product line, sound insulation and motor noise improves, until you’ve reached the top models, which are the very quietest while also being the most powerful. Styrofoam, rubber, and smoother-running motors all contribute to noise reduction.
Do not, however, confuse the sound of the sink vibrating with noise from the disposal. Depending on the material the sink is made of, it may vibrate a lot or a little, and that noise is entirely independent from the noise levels of the disposals themselves.


Disposals are priced anywhere from $70-$350. As the price goes up, the materials improve, motors become more powerful, noise levels decrease, and warranties grow longer. A decent disposal will cost around $100. A very good disposal will cost around $150-$170. A disposal with optimal sound dampening, peak power, and the longest warranties will be $180-$250.
With disposals, the old saying “you get what you pay for” is absolutely true. For this unsung hero of the kitchen, I recommend investing as much as you can comfortably afford (usually about $20-$40 higher than you originally planned). That $20-$40 will translate to greater satisfaction and better performance. When you break it down over the years you’re using it, the price difference comes out to about a penny a day over the course of ten years.
Don’t give your house indigestion; give it a good disposal and keep its pipes running smooth and clean. You’ll be happy you did!

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