Garbage Disposal Installation Guide

Electrical requirements, mounting systems, drain connections, and dishwasher knockout

Garbage Disposal Overview

A garbage disposal (also called a disposer or garburator) is an electrically powered device installed under a kitchen sink that grinds food waste into small particles that can pass through plumbing. Proper installation requires attention to electrical safety, secure mounting, correct drain connections, and integration with dishwasher drainage if applicable.

Most disposals use one of two mounting systems: the traditional 3-bolt mount or the newer EZ mount/quick lock system. Understanding your mounting type and having the correct tools makes installation straightforward, typically taking 1-2 hours for a replacement or 2-3 hours for a new installation.

Important: Always turn off power at the circuit breaker before beginning any electrical work. Test with a voltage tester to confirm power is off. If you're uncomfortable with electrical work, hire a licensed electrician for that portion.

Electrical Requirements

Two Common Wiring Configurations

Option 1: Dedicated Circuit (Most Common)

• Disposal hardwired directly to a dedicated 15A or 20A circuit
• Controlled by wall switch above counter
• Power runs through switch to disposal
• Most professional installations use this method
• Switch should be clearly labeled "Disposal"
• Requires junction box or direct wire connection under sink

Option 2: Switched Outlet

• Disposal plugs into outlet under sink
• Outlet controlled by wall switch above counter
• Easier to disconnect for service
• Common in newer installations
• Disposal must have power cord (sold separately if not included)
• Can share circuit with other non-motor loads (check local codes)

Electrical Specifications

Disposal Size	Typical Amperage	Recommended Circuit	Notes
1/3 - 1/2 HP	5-7 amps	15A circuit	Light use, 1-2 people
3/4 HP	8-10 amps	15A or 20A circuit	Medium use, 3-4 people
1 HP	11-13 amps	20A circuit recommended	Heavy use, 5+ people

Electrical Safety: All electrical work must comply with National Electrical Code (NEC) and local codes. The disposal must be grounded. GFCI protection requirements vary by jurisdiction - check local codes. Always turn off power at the breaker before working on electrical connections.

Wiring a Disposal with Power Cord (Plug-in Installation)

Remove electrical cover plate on disposal (usually bottom or side)
Install strain relief connector in the electrical knockout hole
Feed power cord through strain relief leaving 6-8" of wire inside
Connect wires: Black to black, white to white, green to green ground screw
Use wire nuts to secure connections and wrap with electrical tape
Tighten strain relief to secure cord
Replace electrical cover plate
Plug into switched outlet and test

Mounting Ring Systems

Garbage disposals attach to the sink drain opening using one of two mounting systems. Both are secure when properly installed, but the process differs significantly.

Mounting System Comparison

System Type	Brands	Installation Method	Pros/Cons
3-Bolt Mount	InSinkErator	Mounting ring, fiber gasket, 3 screws tightened with screwdriver	Very secure, requires helper to hold disposal while tightening
EZ Mount / Quick Lock	Waste King, Moen, KitchenAid	Mounting assembly, twist disposal to lock	Easier solo install, quick removal for service

3-Bolt Mount Installation Steps

Apply plumber's putty around sink flange, insert into drain hole from above
From below, slide fiber gasket, backup ring, and mounting ring onto flange
Install snap ring into groove on sink flange to secure mounting assembly
Tighten three mounting screws evenly in a star pattern to secure assembly
Remove excess putty from around flange above sink
Lift disposal and align mounting tabs with mounting ring slots
Support disposal weight (use helper or stack items under it)
Rotate disposal clockwise until mounting ears engage
Tighten mounting screws on disposal to lock it in place
Check that disposal is secure and level

EZ Mount Installation Steps

Apply plumber's putty around sink flange
Insert flange into drain hole from above
From below, place rubber gasket, mounting ring, and backup plate onto flange
Thread mounting nut onto flange and tighten with wrench
Remove excess putty from above
Lift disposal and align with mounting assembly
Rotate disposal clockwise until it locks into place with a click
Verify disposal is secure - it should not rotate when twisted

Pro Tip: When installing solo, place a piece of 2×4 or other support under the disposal to hold its weight while you secure the mounting. This frees both hands for aligning and tightening.

Drain Pipe Connections

Understanding Disposal Drain Configuration

Garbage disposals discharge ground waste through the side outlet. This must connect to your drain system properly to prevent leaks and ensure proper drainage. The configuration depends on whether you have a single or double bowl sink and whether a dishwasher is present.

Common Drain Configurations

Single Bowl with Disposal Only

• Disposal outlet connects directly to P-trap
• Use disposal drain elbow (usually included) and slip joint connections
• Ensure proper slope downward toward trap
• P-trap connects to wall drain or floor drain

Single Bowl with Disposal and Dishwasher

• Dishwasher drain hose connects to disposal's dishwasher inlet (small nipple on side)
• MUST remove dishwasher knockout plug before connecting (see below)
• Dishwasher drain must have high loop or air gap per code
• Disposal outlet connects to P-trap as normal

Double Bowl Sink with Disposal in One Basin

• Disposal typically installed in bowl without dishwasher drain
• Other bowl has standard basket strainer
• Both drains connect to a continuous waste tee or baffle tee
• Tee assembly then connects to single P-trap
• Dishwasher (if present) connects to disposal side

Connecting Drain Pipes

Measure and cut pipes to needed lengths using hacksaw or PVC cutter
Deburr cut edges with utility knife or sandpaper
Slide slip joint nuts and washers onto pipes before assembly
Insert pipe into fitting - hand tighten slip joint nut
Tighten nuts an additional 1/2 turn with slip joint pliers (don't overtighten)
Ensure all connections slope downward toward drain
Support long horizontal runs with pipe straps
Test for leaks by running water and disposal

Drain Pipe Sizing

Component	Standard Size	Notes
Disposal outlet	1-1/2"	Standard for all disposals
Drain tailpiece	1-1/2"	Connects disposal to trap or tee
P-trap	1-1/2"	Matches drain pipe size
Waste tee (double sink)	1-1/2"	Combines two drains
Wall drain stubout	1-1/2" or 2"	May need adapter if sizes differ

Code Requirement: All drain connections must have proper venting per plumbing code. Most kitchen sinks are vented through the main stack. If you're relocating a sink or adding a disposal where none existed, verify proper venting with local building inspector.

Dishwasher Drain Knockout Removal

CRITICAL STEP: If you have a dishwasher, you MUST remove the knockout plug from inside the disposal before connecting the dishwasher drain. Forgetting this step is a common mistake that prevents the dishwasher from draining and can cause water backup.

Do Not Skip This Step! The knockout plug is a solid plastic disc that blocks the dishwasher inlet port from the inside. It MUST be removed and retrieved before using the disposal with a dishwasher.

Knockout Removal Steps

Before mounting disposal, locate the dishwasher inlet nipple on the side (smaller than main drain outlet)
Place disposal on its side on a stable surface
Insert flathead screwdriver into dishwasher inlet from the outside
Tap screwdriver firmly with hammer to knock the plug into the disposal cavity
Reach into disposal from top and retrieve the knocked-out plug
Verify plug is completely removed - shine flashlight to check the opening is clear
Do NOT proceed without retrieving the plug - it can damage disposal or clog drain

Connecting Dishwasher Drain

Connect dishwasher drain hose to disposal inlet nipple using hose clamp
Hose must have "high loop" - secured to underside of countertop near top of cabinet
Alternative: Install air gap on sink deck (required in some jurisdictions)
Ensure hose has no kinks and slopes properly toward disposal
Use stainless steel or all-metal hose clamps (not plastic spring clamps)
Tighten clamp securely but not so tight that it damages the hose

High Loop vs. Air Gap

High Loop

• Dishwasher drain hose secured to underside of counter
• Loop must be as high as possible
• Prevents backflow from disposal to dishwasher
• Acceptable in most jurisdictions

Air Gap

• Physical air gap installed on sink deck or counter
• Prevents any possibility of backflow
• Required by code in some areas
• More visible but provides superior protection

Reset Button and Jam Clearing

Reset Button (Overload Protection)

All garbage disposals have a built-in overload protector that shuts off power if the motor overheats or draws too much current. This prevents motor damage from jams or overuse.

Reset button located on bottom of disposal (red or black button)
If disposal hums but doesn't grind, motor may be jammed or overloaded
Turn off disposal and wait 5-10 minutes for motor to cool
Press reset button firmly - you should feel it click
If button won't stay pressed, motor needs more cooling time
After reset, try disposal again - clear jam if needed (see below)

Clearing a Jammed Disposal

Turn off power at breaker - NEVER put hands in disposal with power on
Shine flashlight into disposal to locate obstruction
Use pliers or tongs to remove visible objects (never hands)
Insert hex key (Allen wrench) into hex socket on bottom of disposal
Turn hex key back and forth to manually rotate grinding mechanism
Work obstruction loose until disposal rotates freely
Remove hex key and press reset button
Restore power and test disposal with water running

Hex Key Included: Most disposals include a hex key (Allen wrench) for jam clearing. It's typically 1/4" and may be stored in a holder on the disposal. If lost, a standard 1/4" hex key from a hardware store works.

Common Disposal Problems and Solutions

Problem	Likely Cause	Solution
Disposal hums but won't turn	Jammed grinding mechanism	Clear jam with hex key, press reset
No sound at all	No power or tripped reset	Check breaker, press reset button
Leaking from top/sink connection	Loose mounting or bad putty seal	Tighten mounting or remount with fresh putty
Leaking from side connections	Loose drain pipes or dishwasher hose	Tighten connections, check gaskets
Leaking from bottom	Failed internal seal (not repairable)	Replace disposal
Dishwasher not draining	Knockout plug not removed	Remove disposal and knock out plug
Loud rattling noise	Foreign object in grinding chamber	Turn off power, remove object with pliers

Disposal Sizing by Household

Choosing the right disposal size (horsepower) depends on household size, cooking frequency, and budget. Larger motors grind faster, handle tougher waste, and are quieter.

Motor Size	Best For	Price Range	Features
1/3 HP	1-2 people, light use	$50-$100	Basic, slower grinding, louder
1/2 HP	2-3 people, moderate use	$80-$150	Good balance of price and performance
3/4 HP	3-5 people, regular use	$150-$250	Faster, handles tougher waste, quieter
1 HP	5+ people, heavy use, large households	$250-$400+	Commercial-grade, very quiet, longest life

Additional Features to Consider

Sound Insulation

Multi-layer insulation reduces noise
More expensive models significantly quieter
Anti-vibration mounts help

Grinding Components

Stainless steel grinding components last longer
Multiple grinding stages reduce particle size
Anti-jam features in premium models

Warranty

Budget models: 1-2 year warranty
Mid-range: 3-5 year warranty
Premium: 5-10 year or lifetime warranty

Septic System Safe

Some disposals designed for septic systems
Bio-charge or enzyme cartridges available
Check with septic professional first

Step-by-Step Installation Process

Turn Off Power

Shut off power at the circuit breaker. Test with voltage tester to confirm power is off. If replacing existing disposal, disconnect and remove old unit.

Remove Dishwasher Knockout (If Applicable)

If you have a dishwasher, knock out the plug from the dishwasher inlet and retrieve it from inside the disposal. Do not skip this step!

Install Mounting Assembly

Apply plumber's putty to sink flange and install mounting assembly from below. Tighten according to your mounting system (3-bolt or EZ mount).

Connect Electrical

Either hardwire directly or install power cord and plug into switched outlet. Ensure proper grounding and use wire nuts for all connections.

Mount Disposal

Lift disposal and attach to mounting assembly. Use support under disposal or a helper. Rotate or tighten until disposal is secure and level.

Connect Drain Pipes

Attach drain elbow to disposal outlet. Connect to P-trap and wall drain using slip joint connections. Ensure proper slope and support.

Connect Dishwasher Drain (If Applicable)

Attach dishwasher drain hose to disposal inlet with hose clamp. Ensure high loop or air gap is properly installed per code requirements.

Test for Leaks

Restore power. Run cold water and turn on disposal. Check all connections for leaks. Run dishwasher through drain cycle if applicable. Tighten connections if needed.

Tools and Materials Needed

Essential Tools

Screwdriver set (flathead and Phillips)
Slip joint pliers or channel locks
Hammer
Hex key (usually included with disposal)
Voltage tester
Wire strippers/cutters
Hacksaw or PVC cutter
Putty knife
Adjustable wrench
Flashlight
Bucket and towels

Materials

Garbage disposal
Power cord (if not included/hardwired)
Plumber's putty
Drain pipes and fittings (if needed)
Wire nuts and electrical tape
Hose clamp (for dishwasher connection)
Teflon tape
Slip joint washers/gaskets
Mounting hardware (usually included)

Safety and Code Considerations

Electrical Safety: ALWAYS turn off power at the breaker before working on disposal electrical connections. Use a voltage tester to confirm power is off. If uncomfortable with electrical work, hire a licensed electrician.

Never Put Hands Inside: NEVER put your hands into a garbage disposal, even with power off. Use tongs or pliers to remove objects. Motors can start unexpectedly if reset button is bumped or someone turns on switch.

Heavy Unit: Garbage disposals weigh 15-25 pounds and are awkward to maneuver. Use proper lifting technique or ask for help. Support disposal while making mounting connections.

Proper Grounding Required: Disposal must be properly grounded per electrical code. Green or bare copper ground wire must be connected to green ground screw on disposal. Do not omit ground connection.

Note: Local electrical and plumbing codes vary. Some jurisdictions require GFCI protection, specific venting, or professional installation. Check with local building department before beginning work. Permit may be required for new installations.

Quick Reference Summary

Installation Checklist

Power off at breaker, verified with tester
Dishwasher knockout removed (if applicable)
Mounting assembly secure and level
Electrical properly connected and grounded
Disposal mounted securely
Drain pipes connected with proper slope
Dishwasher high loop or air gap installed
All connections tested for leaks

Common Mistakes to Avoid

❌ Forgetting to remove dishwasher knockout
❌ Not retrieving knockout plug from inside
❌ Overtightening drain connections (causes leaks)
❌ Omitting ground wire connection
❌ No high loop for dishwasher drain
❌ Mounting disposal before testing electrical

Disclaimer: This guide provides general information about garbage disposal installation. Always follow manufacturer instructions specific to your model. Local electrical and plumbing codes must be followed. If you're uncomfortable with electrical work, hire a licensed electrician. Check local codes regarding permits, GFCI requirements, and disposal use with septic systems.