Yes, you can plumb a kitchen sink with a garbage disposal yourself if you have basic plumbing skills and the right tools. This guide will walk you through kitchen sink plumbing and garbage disposal plumbing step-by-step, making drain installation garbage disposal manageable for most DIY enthusiasts. We’ll cover everything from connecting plumbing to disposal to plumbing a double sink disposal, ensuring a smooth and leak-free setup.
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Getting Started: What You Need for Garbage Disposal Plumbing
Before diving into kitchen plumbing basics, gather your tools and materials. Having everything ready makes the process much smoother.
Tools You’ll Need
- Adjustable Wrenches: Essential for tightening and loosening various fittings.
- Pipe Wrench: Good for stubborn pipes, but use with care to avoid damaging plastic.
- Plumber’s Putty: Creates a watertight seal around the sink flange.
- Teflon Tape (Pipe Thread Sealant): Seals threaded pipe connections.
- Bucket: For catching any residual water.
- Screwdriver Set: For securing clamps and other components.
- Hacksaw or PVC Cutter: To cut drain pipes to the correct length if needed.
- Safety Glasses: Protect your eyes from debris and water.
- Gloves: Keep your hands clean and protected.
- Flashlight or Headlamp: For visibility under the sink.
- Old Towels or Rags: For cleaning up spills.
Materials You’ll Need
- Garbage Disposal Unit: Choose one that fits your needs and sink type.
- Sink Flange: Usually comes with the disposal, but check your specific model.
- Mounting Assembly: Also typically included with the disposal.
- Drain Pipe (Tailpiece): Connects the sink drain to the disposal.
- P-Trap Assembly: Essential for preventing sewer gases from entering your kitchen. This includes the trap itself and various fittings.
- Drain Elbow: A 90-degree elbow to connect the disposal outlet to the P-trap.
- Dishwasher Drain Hose Connector: If you plan to connect your dishwasher.
- Clamps: For securing the dishwasher hose and drain pipe connections.
- Drain Pipe for Main Drain Connection: If you’re not connecting directly to an existing P-trap.
Preparing Your Kitchen Sink for Disposal Installation
Proper preparation is key to a successful drain installation garbage disposal.
Removing the Old Drain Assembly
- Clear Under the Sink: Remove everything from the cabinet beneath your kitchen sink to give yourself ample working space.
- Place a Bucket: Position a bucket directly under the existing drain pipe and P-trap to catch any water that may be trapped.
- Loosen the Slip Nuts: Use an adjustable wrench to loosen the slip nuts connecting the tailpiece and the P-trap to the sink drain and the wall drain pipe. Turn them counter-clockwise.
- Remove the Old Drain and Trap: Once the nuts are loose, gently pull the old drainpipe and P-trap away. Some residual water might spill, so have rags ready.
- Remove the Old Sink Flange: Inside the sink basin, you’ll see the metal or plastic sink flange. Look underneath the sink where the flange meets the sink. There’s usually a large locking ring or a series of screws holding it in place. Unscrew or release these to remove the old flange. Clean any old plumber’s putty or sealant from the sink opening.
Cleaning the Sink Opening
Ensure the sink opening is clean and free of any old putty, sealant, or debris. A clean surface is crucial for a good seal with the new sink flange garbage disposal.
Installing the New Sink Flange
The sink flange garbage disposal is the gateway for waste into your disposal.
- Apply Plumber’s Putty: Roll a rope of plumber’s putty (about the thickness of a pencil) and press it firmly around the underside of the new sink flange. This creates a watertight seal between the flange and the sink basin.
- Insert the Flange: Push the plumber’s putty-covered flange down into the sink opening from the top.
- Assemble the Mounting Rings: From underneath the sink, slide the rubber gasket, fiber gasket, and then the backup flange (these parts usually come with your disposal’s mounting hardware) onto the sink flange.
- Secure the Flange: Attach the mounting ring that came with your disposal. Use the provided screws or the snap ring mechanism (depending on your disposal model) to firmly secure the mounting assembly to the sink flange. Tighten the screws evenly, alternating between them, to ensure a snug and even fit. This compression will squeeze out excess plumber’s putty around the flange inside the sink.
- Clean Up Excess Putty: From inside the sink, use your finger or a putty knife to wipe away any excess plumber’s putty that squeezed out around the flange.
Connecting Plumbing to Disposal: The Drain Assembly
Now, let’s focus on connecting plumbing to disposal and creating the drain path.
Attaching the Disposal Unit
Most garbage disposals attach to the mounting assembly you just installed using a twist-lock mechanism.
- Lift the Disposal: Carefully lift the garbage disposal unit up to the mounting assembly.
- Align the Grooves: Look for the alignment grooves on the top of the disposal and the corresponding tabs on the mounting ring.
- Twist to Lock: Push the disposal up firmly and turn it clockwise until it locks into place. You might hear or feel a click. Ensure it’s securely seated.
Attaching the Disposal’s Discharge Tube
The disposal has an outlet where the ground food waste exits. This is where your drain piping will connect.
- Knock Out Plug (If Applicable): If this is a new installation and you’re connecting a dishwasher, there’s a knockout plug inside the dishwasher inlet port on the disposal. You must knock this out before using the dishwasher connection. Use a screwdriver and a hammer to gently tap the plug inward. It will fall into the disposal chamber. Remove it from the chamber before running the disposal. If you’re not connecting a dishwasher, leave this plug in place.
- Attach the Discharge Elbow: Most disposals come with a discharge elbow or you’ll use a standard 90-degree PVC elbow. Apply Teflon tape to the threads of the disposal outlet. Screw the elbow onto the disposal outlet clockwise. Tighten it securely with an adjustable wrench, but be careful not to overtighten and crack the plastic.
Installing the Sink Trap Garbage Disposal (P-Trap)
The P-trap is crucial for garbage disposal plumbing. It prevents sewer gases from coming back up through your drains.
- Assemble the P-Trap: Connect the P-trap components. This usually involves a U-shaped bend and two straight pieces (tailpieces). Ensure the rubber gaskets are in place on all slip joints.
- Connect the Disposal Elbow to the P-Trap: Connect the 90-degree elbow from the disposal to the inlet of the P-trap. You might need a short tailpiece here. Slip nuts and gaskets are used to join these pieces. Hand-tighten first, then give a quarter-turn with a wrench.
- Connect the P-Trap to the Wall Drain: Connect the outlet of the P-trap to your existing drainpipe in the wall. Again, use a slip nut and gasket. Hand-tighten, then snug it with a wrench.
Table: Typical P-Trap Components and Their Functions
| Component | Function | Connection Method |
|---|---|---|
| Inlet Tailpiece | Connects disposal elbow/drain to P-trap inlet | Slip nut and gasket |
| Trap Bend | Holds a water seal to block sewer gases | Slip nuts and gaskets |
| Outlet Tailpiece | Connects P-trap outlet to the wall drain pipe | Slip nut and gasket |
| Slip Nuts | Threaded rings that tighten connections | Screw on by hand, then wrench |
| Gaskets (Washers) | Rubber rings that create a watertight seal at slip joints | Sit inside slip nuts |
The Dishwasher Connection Garbage Disposal
If you have a dishwasher, it needs to drain into your plumbing system. The most efficient way is to connect it directly to the garbage disposal.
Connecting the Dishwasher Drain Hose
- Locate the Dishwasher Inlet: On the side of your garbage disposal unit, there’s an inlet port specifically for the dishwasher drain.
- Remove the Knockout Plug (If Not Done Already): If you haven’t already, and you have a dishwasher, use a screwdriver and hammer to carefully tap out the knockout plug from the inside of this port. Make sure to retrieve the plug from the disposal’s grinding chamber.
- Attach the Dishwasher Hose: Slide the dishwasher drain hose over the disposal’s inlet port.
- Secure with a Clamp: Use a hose clamp to tightly secure the dishwasher drain hose to the port. This prevents the hose from popping off during the dishwasher’s drain cycle, which could cause a flood.
- Create a High Loop: Before connecting the hose to the disposal, it’s good practice to create a “high loop.” This means routing the dishwasher hose up as high as possible under the sink before it drops down to the disposal. Secure this loop with a zip tie or hook. This high loop acts as a backup to prevent dirty water from the disposal or sink from backing up into the dishwasher.
Plumbing a Double Sink Disposal
If you have a double sink, plumbing a double sink disposal requires a slightly different approach. You’ll need a double sink drain assembly.
- Install the Sink Flanges: Install a sink flange in each basin of your double sink, following the same steps as for a single sink.
- Connect the Tailpieces: Attach a tailpiece to each sink flange.
- Install the Double Sink Drain Assembly: A double sink drain assembly typically includes a cross-shaped fitting or two pipes that connect to a central Y-fitting.
- Connect the tailpiece from one sink basin to one inlet of the cross-fitting or Y-fitting.
- Connect the tailpiece from the other sink basin to the other inlet.
- The third outlet of the Y-fitting (or the main outlet of the cross-fitting) will connect to your disposal’s inlet.
- Connect to the Disposal: Attach a short piece of pipe (tailpiece) from the central Y-fitting or cross-fitting to the garbage disposal’s inlet.
- Complete the Drain System: From the disposal’s discharge outlet, install the elbow, P-trap, and connect to your main drainpipe as you would for a single sink.
Table: Double Sink Drain Setup
| Item | Connects To |
|---|---|
| Sink 1 Tailpiece | Double Sink Drain Assembly (Inlet 1) |
| Sink 2 Tailpiece | Double Sink Drain Assembly (Inlet 2) |
| Double Sink Assembly | Garbage Disposal Inlet |
| Disposal Outlet | 90-degree Elbow |
| Elbow | P-Trap |
| P-Trap | Main Drainpipe in Wall |
Waste King Installation and Other Disposal Brands
While the general principles of garbage disposal plumbing are similar across brands like Waste King, Moen, InSinkErator, and others, there can be minor differences in mounting hardware or specific connection types.
- Waste King Installation: Waste King disposals often use a “EZ Mount” system which is a simpler twist-on mechanism. Familiarize yourself with the specific mounting hardware that comes with your model.
- Mounting Ring: Ensure the mounting ring and gasket system are correctly assembled and seated.
- Connections: Always check your disposal’s manual for the exact specifications of its inlet and outlet connections. Most use standard 1.5-inch or 1.75-inch pipe sizes for drain connections.
Testing for Leaks
This is a critical step after connecting plumbing to disposal.
- Initial Check: Before running water, visually inspect all the slip nuts and threaded connections you’ve made. Ensure they are snug.
- Fill the Sink: Fill the sink basin(s) with water. Let it sit for a few minutes.
- Check for Leaks: Place paper towels or dry rags under each connection point and the disposal itself. Look for any drips or wet spots. Tighten any leaking connections slightly.
- Run Water: Now, slowly run cold water into the sink. Let the water drain.
- Run the Disposal: Turn on the cold water and then briefly turn on the garbage disposal for a few seconds to ensure it operates smoothly and there are no leaks around its housing or connections.
- Check Again: Once the water has drained and the disposal has run, check all connections one last time for any signs of moisture.
Frequently Asked Questions (FAQ)
Q1: Can I connect my dishwasher to the garbage disposal if the knockout plug is already removed?
A1: No, if the knockout plug has already been removed, you cannot connect your dishwasher. You would need a new garbage disposal unit with an intact knockout plug for the dishwasher inlet.
Q2: Do I need Teflon tape on all the plastic drain pipe connections?
A2: Teflon tape is primarily for threaded metal or plastic pipe connections. For slip joint connections (those with slip nuts and rubber gaskets), Teflon tape is not used. The gasket creates the seal.
Q3: What kind of water should I run with the garbage disposal?
A3: Always run cold water with your garbage disposal. Cold water helps solidify grease and fats, making them easier for the disposal to grind and flush away, rather than coating the pipes.
Q4: My disposal is making a humming noise but not grinding. What should I do?
A4: This usually means the grinding mechanism is jammed. First, ensure the unit is turned OFF at the switch and the power is disconnected at the breaker. Then, locate the reset button on the bottom of the disposal. Press it. If it still hums, use a hex wrench (often provided with the disposal) inserted into the center hole on the bottom of the unit to manually rotate the grinding plate back and forth to dislodge the obstruction. Once clear, restore power and try again.
Q5: What is the purpose of the P-trap in garbage disposal plumbing?
A5: The P-trap is designed to hold a small amount of water, creating a seal that prevents foul-smelling sewer gases from rising through the drain and into your kitchen.
Final Thoughts on Kitchen Sink Plumbing with a Disposal
Installing a garbage disposal is a rewarding DIY project that enhances your kitchen’s functionality. By following these steps carefully, and paying close attention to each connection, you can achieve a professional-quality installation. Remember to always prioritize safety, work methodically, and consult your specific disposal unit’s manual for any brand-specific instructions. With a little patience and the right approach to kitchen sink plumbing and garbage disposal plumbing, you’ll have your new disposal up and running in no time!