An overview of disposers, including when to replace, specifying, maintenance considerations and energy efficiency concerns.

 Disposers: An Overview

All disposers handle the same type of waste, but horsepower determines the operational capacity and volume. Here’s a quick look at how disposers work, what they are made of and more.

Most basic commercial disposers are scaled up versions of residential types and range from 1/2 to 10 HP. Foodservice operators can choose from other types and sizes for specific applications.

Materials vary by manufacturer, but all disposers feature an easy-to-clean corrosion-resistant finish. Housing construction can be aluminum, stainless steel or cast iron that may be coated or plated. A majority of the cutting mechanisms available are made of rust-resistant nickel, stainless steel or austempered heavy ductile iron. The basic disposer design has not significantly changed in a long time but newer control systems can reduce water and energy consumption.

Disposers with rotor-fixed cutting teeth represent the most common units but operators can also purchase units with swivel cutting teeth or a hammer mill grinder. All types of disposers include a cutter operating at high speed inside a stationary shredder ring.

Operators can choose from models with varying horsepower, voltage, sizes and type of sink and mount, and control systems. Controls range from basic start/stop operation to electronics that reduce water and energy use and automatically reverse the cutting teeth to maximize service life. More advanced disposers provide the ability to determine when water is needed and can even turn the system off if the operator is not present.

Operators often purchase disposers as a package that also includes the controls, sink or sink mount for existing sinks, stopper, water inlet hardware, back flow preventer, solenoid valve and flow control. Systems featuring a sink assembly mount to the bottom of the sink and include weld-in or bolt-in adaptors. Disposers with a cone assembly incorporate a 12-, 15- or 18-inch stainless steel cone bowl welded into a table.

Voltage options include 115, 208, 230, and 460, with single and triple phase units available. Users can operate disposers with either a standard electrical wall switch or electronic controls. Manual reverse switches can extend the life of the cutting blades, while also unjamming stuck food waste. Automatic reversing controls also are offered.

New customizable, vacuum-based systems collect waste at multiple in-feed stations and deliver it to a single area for bulk processing. Depending on the customer’s intentions for disposal of kitchen waste, these disposers can grind and dewater the waste using a traditional waste pulper; store the waste in a closed tank for removal via a vacuum truck; or deliver it to a bio-degrading system.

 How to Know When to Replace a Disposer

Depending on running time, the type of waste being processed and drain plumbing conditions, a typical disposer can last an average of five years or as long as 20 years. Here are five signs a disposer has reached the end of its service life.

Excessive Noise:Unusual or excessive noise, along with water leakage represent a pair of obvious signs a disposer is failing and needs replacement.

Drain Backups: This may indicate the blade teeth are worn and the mechanism needs replacing or may signify the disposer is on its way out.

Motor Grinding: “If the motor runs and the disposer is jammed up, this puts pressure on the unit,” says Rick Sher, director of service, Day & Nite/All Service in New Hyde Park, N.Y. “When run in this condition, motors can burn up, in which case the disposer will need to be replaced.”

Increased Grind Time: Blades wear out over time and when processing an excessive amount of hard material at high volumes. Signs such as increased grinding time or frequent clogging may signify a new disposer is needed.

Cracks: Over time, the disposer may develop cracks due to excessive use, chemicals and vibrations. Retire the unit when its construction is compromised.

 Disposer Applications

Disposers provide a convenient way to deal with food waste, while improving sanitation in the kitchen and around outside trash containers. Here is a closer look at the way foodservice operators from all industry segments can use this equipment.

Reducing the volume of waste through grinding represents the most common reason to use a disposal system in a commercial kitchen. An uncommon use would be to prepare food only waste for composting or methane gas generating purposes.

Operators sometimes use disposers with other equipment to process food waste in larger volume applications. This makes waste easier to collect for composting, anaerobic digestion or hauling to a landfill. The preferred method varies by municipality based on infrastructure and economic and environmental considerations.

Soiled dish tables, pot/pan sinks as well as in vegetable prep, salad prep and meat prep areas represent the areas where foodservice operators most commonly install this equipment.

While capable of grinding just about anything, manufacturers recommend operators only use commercial grade disposers for edible food waste. Non-edible items like corn husks and oyster shells can cause drain problems. Also, manufacturers do not recommend using disposers for processing large volumes of hard organics, which will more quickly wear down cutting blades over time and cause drain backups.

 Maintaining a Disposer

Although disposers require minimal maintenance, proper use will lengthen the system’s service life. Here are several steps foodservice operators can take to enhance the return on their investment in a disposer.

Disposers are simple to maintain, although some types may require periodic drain service by a plumber. “When maintained properly, disposers have the potential to last a lifetime,” Sher says.

Here are a number of factors to consider in the use and maintenance of disposers.

• Do not use these systems to dispose fat, oil and grease.
• Flushing the drain after use will help prevent clogs. Some controls do this automatically.
• “Grind plates should be periodically checked and cleared to prevent clogs,” Sher says.
• Batch feeding food waste into disposers blocks water, resulting in drain line clogs. To solve this problem, operators should fill a 5-gallon bucket with cold water and run it through the disposer to push waste through.
• After feeding waste through the disposer, run cold water for 10 to 20 seconds to push all of the particles to the main sewer line.
• While some systems just need to be wiped clean, others may include automatic cleaning flush systems that need to be activated on a daily basis.
• Keep non-food items, such as plastics, silverware and straws, away from the disposer, as these will cause jams.
• Use cold water to flush waste, since hot water can melt fat and allow it to solidify and block the drain line.
• “Water needs to be able to flow through the disposer,” Sher says. “As long as this is happening, the unit should work.”

It’s important to keep in mind that a disposer does not replace a dumpster and should never be used with dry waste.

 Spec Check: Disposers

When choosing what type of disposer is best suited for an operation, the waste volume and type of menu items are key factors to consider. Here are four other factors operators should weigh when purchasing a disposer.

Waste Volume: Operators should know the amount of waste they plan to process in a given amount of time when choosing a disposer. Typically, this can be calculated by estimating the number of meals served per day.

Municipality Regulations: “There are some regions where [direct drain] disposer use is prohibited in commercial foodservice applications,” Sher says. For this reason, foodservice operators should check with local zoning or municipal boards to ensure these units are allowed and whether interceptors or grease traps are required.

Size and Horsepower: The type of disposer needed depends on an operation’s size and the amount of waste produced. The more waste that is produced, the higher the horsepower needed for processing. Disposer horsepower ranges from ½ to 10. When in doubt, it’s better to go bigger rather than smaller to ensure the amount of waste can be handled.

Waste Disposal Method: In addition to local code requirements, it is critical to consider waste disposal intentions, which may include pulping and truck removal.

Size and Location: When specifying a disposer, operators need to figure out where the unit will be located. For example, a vegetable prep area will require a smaller disposer than a soiled dish table. Choose equipment that will be compatible with the size of dish machine being used. When replacing these units, changing the size or brands may cause additional plumbing or electrical expenses. 

Drain Line Size: The drain line size should be considered, to ensure efficient operation and help circumvent sink backups. Some manufacturers provide free site surveys to ensure the disposer’s drain line can handle the foodservice operation’s waste.

 Energy Efficiency and Disposers

Most disposers are fresh-water systems, which command extensive operating costs. Here are a few energy-efficient features some of these systems feature.

Although disposer flow rates can be more than 10 gallons per minute, when used in conjunction with pulpers and compactors, these systems can offer substantial savings in water use, sewage costs and waste removal charges.

Newer disposer models offer recirculated water operation, vacuum technologies and water-saving flow controls, which can help reduce the operating costs.

Automated, self-contained waste handling systems can substantially reduce foodservice waste and water usage.

At least one manufacturer offers an integrated disposal system for organic kitchen waste. This waterless pulping system disposes of food waste using automated vacuum technology. A myriad of sizes and configurations for high-volume dish room applications is available that can provide up to an 85 percent reduction in food waste volume.