Spec Check: Disposers

Commercial disposers provide a convenient way to deal with food waste while improving sanitation in the kitchen and around outside trash containers. These units help reduce dumpster garbage odors, which can attract insects and vermin and compromise sanitation efforts. Disposers also help lower garbage hauling costs by decreasing the amount of overall waste a foodservice operator dumps.

Foodservice operators often purchase disposers as a package that includes the control, sink or sink mount for existing sinks, stopper, water inlet hardware, back flow preventer, solenoid valve and flow control.

In general, foodservice operators install disposers on soiled dish tables, pot/pan sinks and in vegetable, salad and meat prep areas. While a commercial disposer can grind most items, manufacturers recommend using these units to process edible food waste only. Non-edible food remnants, such as corn husks and seafood shells, typically cause drain clogs.

Although the basic disposer design remains similar from years past, operators can choose from a variety of types and sizes. These systems also offer a choice in voltage, mounting and controls. Controls range from a manual basic start/stop operation to electronic versions that reduce water and energy use and automatically reverse the cutting teeth to maximize the service life. A few energy-saving models have the ability to determine when water is necessary and can turn the system off if the operator is not present.

Construction materials vary between manufacturers, but most disposers have an easy-to-clean, corrosion-resistant finish. Disposer housing construction options include aluminum, stainless steel and cast iron, which can be either coated or plated.

Also, disposers feature different types of cutting mechanisms made from rust-resistant nickel, stainless steel or
austempered heavy ductile iron. Disposers with rotor-fixed cutting teeth represent the most common units on the market, though operators can specify units with swivel cutting teeth or a hammer mill grinder. All three types include a cutter operating at high speed inside a stationary shredder ring.

Voltage options include 115, 208, 230 and 460, with single and triple phase units available. Foodservice operators can choose from either a standard electrical wall switch or electronic controls.

It's important to note the disposal of any effluent into municipal waste water systems is typically governed under municipal by-laws/ordinances and enforced at the local level or through a regional municipal authority, in accordance with state and federal environmental legislation. These municipal ordinances set out allowable limits of various materials and chemicals that can be present in effluent that is being disposed of into the municipal waste water system, and that ultimately need to be processed and treated at the waste water treatment plant.

Specifying Considerations

  • The overall goals of the disposer need to be taken into account, which will determine the size and type of system that best suits a specific foodservice operation. This may include saving time with waste processing and disposing, minimizing odors in waste receptacles or decreasing garbage hauling costs.
  • These units are generally specified by horsepower, which ranges from ½ to 10.
  • An operation's size and amount of waste processed in a given amount of time will dictate the disposer size that is necessary. Typically, this can be calculated by table turns, number of seats and the amount of meals served each day.
  • Verify the type of waste the unit will process to calculate the appropriate horsepower. For small- to medium-sized restaurant kitchens, or vegetable prep areas, salad and pot sink sections of large kitchens, ½ to 1½ hp is recommended. Large kitchens and operations with heavy waste, such as restaurants that offer steak, lobster, ribs or clams, are better suited for disposers offering between 2 and 10 hp.
  • The type of food waste also will determine the type of disposer needed. For example, high-volume operations, or those with waste that is tougher to grind, should consider a disposer that includes a reversing switch that uses both sides of the cutting blade. This feature can double the service life of the unit, saving the operator money over time.
  • Operators also need to verify the number of disposers necessary to properly handle waste-removal requirements. The pot and pan and vegetable prep areas may require individual systems, for example.
  • When specifying, consider the sink configuration and decide if the disposer will be sink, cone or trough mounted. Cone assemblies come in 12-, 15- or 18-inch sizes. Because there are multiple configurations for mounting disposers, the unit type should be appropriate to avoid modifications.
  • The system's throat opening size is another factor to keep in mind. Disposer throats range from 3½ up to 8 inches.
  • Also take into account cost and service life. Operators need to determine whether the operation warrants a cheaper disposer that will be replaced when it fails or a more expensive, heavy duty model that will be serviced and utilized for a longer period.
  • To ensure efficient operation and help circumvent sink backups, foodservice operators need to consider the drain line size in conjunction with the disposer specified. Manufacturers may provide free site surveys to ensure the drain line can handle the disposer waste.
  • Before specifying a disposer, operators should confirm that the necessary plumbing and electrical hookups are available.
  • Disposer systems with manual on/off switches are recommended for smaller operations or those with less food waste, while automatic controls that turn both water and energy off when the disposer is not in use can provide increased energy efficiency for higher volume use.
  • Waste disposal methods, such as pulping and truck removal, also should be taken into account when choosing a disposer to ensure compatibility.
  • Because some regions have regulations that prohibit the use of disposers, operators should check with their local zoning or municipal boards before specifying to confirm that these systems can be utilized.
  • Some areas require food waste to pass through solid interceptors and grease traps before traveling into the sewer. Equipment dealers and disposer manufacturers can provide the necessary information in terms of regulations and requirements.
  • Composting, biodigesting, compactors, scrapping and pulping are other waste disposal options for municipalities that prohibit disposers.

Common Specifying Mistakes

  • Not following manufacturers' recommendations when selecting a disposer can result in an inadequate system for the operation.
  • A common mistake is underestimating the size disposer necessary to handle a foodservice operation's waste needs. Because most operations become more dependent on these systems than expected, it is better to go bigger in terms of horsepower to ensure the waste amount can be accommodated.
  • Not specifying systems with manual or automatic reversing controls in high-volume operations can compromise the life of the cutting blades, while also leading to jammed food waste.
  • Consider protection devices when there is a high probability of foreign material, like cutlery, getting stuck in the disposer. In this case, systems with screens or magnets are best used to prevent these items from getting into the system.
  • Disposers are not designed to handle large batches of food waste, which will block water and result in drain clogs.
  • Disposers may not be suitable for operations with menus mainly consisting of food waste that creates sediment, such as oyster shells, as these can build up in the drain line and result in jams. A high concentration of fibrous materials, like corn husks, can potentially cause drain obstructions. 
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