The top 5 things a plumbing contractor should know about food-waste disposers
Picking up a nugget or two will further reinforce your image as a disposer and plumbing expert.
It’s a pretty sure bet that as a contractor, you already know more than most homeowners about foodwaste disposers (aka garbage disposals or garburators in Canada).
But every now and then a question comes out of left field, and with that in mind, we present the top five things you should know about disposers. Think of it as a handy refresher and you just might pick up a nugget or two that will further reinforce your image as a disposer and plumbing expert the next time you’re asked something pertinent to the job — or not.
1. The best reasons to have a disposer
Since garbage disposers grind food to less than 1/4-inch, in size, they are safe for household and municipal pipes. Homeowners with and without disposers should be counseled to never put grease or fats down any drain to avoid plumbing problems.
Not only does a garbage disposer in the kitchen sink mean less bagged waste in the household, fewer odors, insects and pests and greater hygiene — a disposer is good for the environment, too.
Similar to composting, a disposer keeps food waste out of landfills, a significant source of greenhouse gas emissions. But a disposer also can provide an environmentally responsible alternative to transporting food waste to landfills because it sends food waste to a wastewater treatment plant or septic system.
Many wastewater treatment plants can turn food scraps sent by disposers into renewable energy and/or fertilizer. Composting is great and disposers complement composting by grinding food waste that shouldn’t be composted such as meat and dairy products.
At capable treatment plants, food waste is recycled into renewable energy, while biosolids, a byproduct of the treatment process, can be converted into fertilizer. This is an environmentally responsible option.
Here’s something else homeowners will be surprised to know. Disposers use a minimum amount of water and electricity. On average, disposers use about 1 gallon of water per person per day. That is 1% or less of a household’s total water consumption. Disposers use about 3 to 4 kilowatt hours of electricity. On average, that’s less than 50 cents a year for operation.
2. How a disposer works; one fact to surprise them
There are many myths surrounding disposers; however, let’s put the biggest one to rest. There are no blades. A disposer works more like a cheese grater than a blender and shreds/grinds food waste rather than cutting. It does not slice or cut as a blender or food processor would.
When food waste is placed in a disposer, it lands on a turntable spinning at high speed. Centrifugal force and the impellers (or lugs) attached to the turntable push the food waste against a stationary shredder ring. The food is ground into small particles so that when mixed with water it safely can flow through plumbing and into the wastewater system or septic tank.
3. All disposers were not created equal
There are two basic disposer types:
• Continuous feed: The continuous feed disposer is the most common type and as the name implies, with it, food waste is fed into the grind chamber continuously while it is grinding.
• Batch feed: The batch feed type allows users to feed food into the grind chamber in batches. When the grind chamber is full, the cover is inserted and turned to activate the motor. This provides the extra assurance of covered operation.
There are two disposer motor types:
• Induction motor: An induction motor is a durable, heavy-duty motor. It is similar to motors used in commercial disposers and household appliances where reliability is critical, such as clothes washers, dryers and furnaces. Induction motors have fewer moving parts than a permanent magnet motor for long, reliable life. Running at a lower RPM (revolutions per minute), induction motors also produce less noise.
Disposers with induction motors operate with higher inertia, which helps reduce the chance of jamming. In addition, some disposers also feature an auto-reverse mechanism that reverses grinding direction upon motor start-up. This helps to prevent jams and ensures grinding elements wear evenly to prolong disposer life. Other disposers may feature jam-sensing technologies that will increase the torque of the induction motor if it senses a jam is eminent.
• Permanent magnet motor: A permanent magnet motor is a variable-speed motor often found in appliances such as hand-held hair dryers and vacuum cleaners. This motor includes brushes that may wear over time. Many permanent magnet motor disposers run at a higher rate of speed which is not required with food-waste disposers and may in fact even hinder effective and complete waste grinding.
4. Disposer features and what they mean
One feature to look at is sink mountings. There are two primary types: the three-bolt stainless steel mount and the threaded ring mount.
The three-bolt mounting system is the most common sink-mounting system on disposers and used in more than 100 million installations. The stainless steel construction with “twist-on, twist-off” design makes secure installations quick and easy.
The threaded mounting system is a lightweight plastic and aluminum system to mount disposers. A threaded support ring attaches the sink flange to the sink. Then a mounting ring attaches the disposer to the flange for installation.
Another feature to look at is electrical connections. Check to see if the disposer is hardwired or has a power cord plugged into an outlet. Depending on the electrical code in your trading area, you will have one installation or the other. Many disposers are sold without an attached power cord so they may be used in either application. If you need a power cord, these can be purchased separately. You may also purchase a unit with an attached power cord.
The third feature to look at is component materials. Stainless steel adds strength while resisting rust and corrosion to help prolong disposer life. Some disposers are constructed with a stainless steel grind chamber and/or stainless steel grind components. Other disposers use galvanized steel grind components. This durable material is long lasting but can rust or corrode over time. Most disposers are constructed with thermoplastic polymer grind chambers which resist rust and corrosion to prolong disposer life.
Then there are the stages of grind. Garbage disposers grind food into less than 1/4-inch, in size, however some disposers feature multiple grind stages so they can grind food waste into even finer food particles. The finer the grind is, the less chance for a potential clog.
Most disposers feature only one stage of grind. Food is ground before passing through drain pipes with water. A 2-stage disposer grinds food in two stages to achieve a finer grind. The second stage of grinding virtually liquefies food waste, allowing for more types of difficult foods to be ground. It also decreases the chance for clogs or jams.
A 3-stage disposer provides the finest grind available, allowing users to grind virtually any food waste including fibrous or hard materials with no worry of clogs or jams. These units will even cut grains of cooked rice into smaller pieces.
Noise level is another feature to look at. Noise from a disposer is primarily caused by the transmission of vibration from the disposer to the sink or countertop as well as the grinding process itself. The majority of disposers do not feature insulation. However, there are some that have sound insulation wrapped around the outside of the disposer body to reduce noise. Other models also feature noise-reducing technologies including: noise-reducing sink baffles, anti-vibration sink mounts and anti-vibration tail pipes to significantly reduce the noise produced by a disposer.
Horsepower and grind capacity also are important features. Disposers have motors which range in horsepower from 1/3 hp to 1.0-plus hp. Higher horsepower disposers typically are capable of grinding heavier loads easier, which prolongs motor life. You might consider higher horsepower models for larger families or frequent cooking.
The grind capacity of a disposer refers to the interior size of the grind chamber which ranges from about 26 oz. to 40 oz. A larger grind capacity allows grinding more food in a single batch.
5. Disposer replacement and installation
Listed below is a brief summary of general installation steps. To brush up on the details, refer to the installation, care and use manual inside the disposer carton for complete installation instructions.
• Remove old disposer: Turn off the electricity to the disposer at the circuit breaker or fuse box. Disconnect the old disposer plumbing connections and remove the disposer from its mounting. Disconnect the old disposer’s electrical connections.
• Make electrical connections: Connect wiring to the new disposer following the code in your area.
• Dishwasher connections: If connecting to a dishwasher, knock out the dishwasher plug. If no dishwasher, leave plug intact.
• Connect new disposer: Mount disposer onto the sink-mount assembly and reconnect plumbing, including the dishwasher hose if applicable. Turn on the electrical power to the disposer at the circuit breaker.
• Make plumbing adjustments: Lock the disposer in place, make final plumbing adjustments and check for any leaks.
Other frequently asked questions you’re likely to encounter
• When running water with a disposer, should it be hot or cold?
Always use cold water. Cold water allows food residue to be easily washed down the drain and should be left running for 10 to 15 seconds after the waste is ground to ensure its dispersal. Cold water also saves on the energy that would otherwise be wasted if it was run until heated.
• What about difficult food items, such as celery, potato peels and bones?
Disposers can handle them. However, it is recommended that users avoid grinding large amounts of food scraps at one time. Remind them to feed the waste into the grind chamber slowly, in moderate amounts and with the water running. Models with multiple grind stages are better equipped to handle these types of food scraps.
• What food items should not be put down a disposer?
Never pour grease or fat down any disposer or drain. It can build up in pipes and cause drain blockages. Tell users to put grease in a jar or can and dispose it in the trash.
Clam shells, oyster shells, lobster, shells and crab shells should not be put into a disposer.
• Is a garbage disposer safe to use with a septic system?
Garbage disposers are compatible with properly sized and maintained septic systems. In fact, some disposers are specifically designed for homes with septic systems. These disposers inject a special solution containing microorganisms into the grind chamber during the grinding process to help break down food waste in the septic tank.
Many more instructional topics also are available at training portals. However, always make certain the video instructions found on publicly available sites are from a reliable source.