How to Connect a Dishwasher to a Garbage Disposal
Updated February 25, 2026
Route the dishwasher drain hose to the garbage disposal inlet with a proper high loop or air gap to prevent backflow and odor.
Overview
The dishwasher drains through the garbage disposal. A drain hose runs from the dishwasher pump to a side inlet on the disposal body. If the disposal is new, you need to knock out the drain plug inside the inlet first -- a step that trips up nearly every first-time installer. The hose must loop up to the underside of the countertop (high loop) or connect through an air gap device before dropping down to the disposal. This loop prevents dirty water from the disposal from flowing backward into the dishwasher.
What You'll Need
Safety First
- Unplug the garbage disposal or turn off the breaker before working on the drain connection. The disposal activates from a wall switch -- an accidental bump starts the motor.
- If the disposal is brand new, knock out the drain plug from the dishwasher inlet BEFORE mounting the disposal. Forgetting this step means the dishwasher cannot drain and you have to remove the disposal to access the plug.
- The drain hose must have a high loop or air gap. Without it, dirty water siphons from the disposal back into the dishwasher, contaminating clean dishes.
Step-by-Step Instructions
- Knock Out the Disposal Drain Plug (New Disposals Only)
New garbage disposals ship with a plastic plug blocking the dishwasher inlet. If you have a dishwasher, this plug must be removed. Insert a screwdriver or wooden dowel into the inlet opening from inside the disposal (looking down through the sink drain). Tap with a hammer to knock the plug into the grinding chamber. Reach in with pliers and remove the plug. If you leave the plug in, the dishwasher has nowhere to drain.
Tip: This is the single most forgotten step in disposal installation. If your dishwasher is not draining after a new disposal install, check the inlet plug first. It takes 30 seconds to fix. - Route the Drain Hose with a High Loop
The dishwasher drain hose exits the dishwasher at the bottom left or right side. Route it to the disposal, but first loop it up as high as possible under the countertop. Secure the highest point of the loop to the underside of the countertop with a zip tie or hose clamp screwed to the cabinet wall. The high point should be at or near the underside of the counter. This high loop prevents backflow -- water cannot siphon backward from the disposal into the dishwasher because it would have to travel uphill over the loop.
Tip: Some plumbing codes require an air gap device instead of a high loop. An air gap is a small chrome fitting mounted on the countertop or sink that the hose routes through. Check your local code. Either method prevents backflow. - Connect the Hose to the Disposal Inlet
Push the drain hose onto the disposal's dishwasher inlet nipple (the small threaded or barbed fitting on the side of the disposal body). Secure with a hose clamp -- tighten the clamp screw until snug. The hose should not pull off under pressure. If the hose is too large for the inlet, use a reducer adapter ($3-$5). If the hose is too short to reach with the high loop, buy an extension hose or a longer replacement hose ($8-$15).
Tip: Use a worm-gear hose clamp (the kind with a screw band), not a spring clamp. Worm-gear clamps provide adjustable, consistent pressure and do not loosen over time. Spring clamps can slip off the ribbed inlet nipple. - Test the Connection
Run the dishwasher on a short cycle. During the drain phase, check under the sink: watch the hose connection at the disposal inlet for drips, check the high loop for kinks, and verify water flows through the disposal and out the drain (run the disposal briefly during the dishwasher drain cycle to clear the discharged water). No drips, no kinks, no backup? The connection is solid.
Tip: If the dishwasher drain water backs up into the sink, the disposal is not running or is clogged. The dishwasher drains INTO the disposal -- if the disposal is full of food waste, the water has nowhere to go. Run the disposal to clear it before running the dishwasher.
Pro Tips
- Always run the garbage disposal before starting the dishwasher. This clears any food waste from the disposal chamber and ensures the dishwasher drain water has a clear path.
- If your sink does not have a garbage disposal, the dishwasher drain hose connects to a tailpiece with a dishwasher inlet branch ($8-$12). The high loop requirement is the same.
- The dishwasher drain hose should be 5/8-inch inner diameter. Using a smaller hose restricts flow and can cause the dishwasher to drain slowly or trigger an error code.
- If the dishwasher is far from the sink (island installation), the drain hose run may be too long for gravity drainage. In that case, a dishwasher drain pump ($30-$50) boosts the water to the disposal or drain connection.
- Replace the dishwasher drain hose every 8-10 years. The rubber degrades from heat (the dishwasher drains at 130-140°F) and develops cracks that leak slowly onto the cabinet floor.
When to Call a Pro
You do not need a plumber for this connection. It is a standard part of dishwasher and disposal installation. Call a plumber only if the disposal does not have a dishwasher inlet (very old or commercial models), if you need an air gap device installed on the countertop (requires drilling a hole in the sink or countertop), or if the drain hose run is exceptionally long and needs a drain pump.
Frequently Asked Questions
When should I call a plumber to connect a dishwasher to a garbage disposal?
You do not need a plumber for this connection. It is a standard part of dishwasher and disposal installation. Call a plumber only if the disposal does not have a dishwasher inlet (very old or commercial models), if you need an air gap device installed on the countertop (requires drilling a hole in the sink or countertop), or if the drain hose run is exceptionally long and needs a drain pump.
What are some expert tips to connect a dishwasher to a garbage disposal?
Always run the garbage disposal before starting the dishwasher. This clears any food waste from the disposal chamber and ensures the dishwasher drain water has a clear path. If your sink does not have a garbage disposal, the dishwasher drain hose connects to a tailpiece with a dishwasher inlet branch ($8-$12). The high loop requirement is the same. The dishwasher drain hose should be 5/8-inch inner diameter. Using a smaller hose restricts flow and can cause the dishwasher to drain slowly or trigger an error code. If the dishwasher is far from the sink (island installation), the drain hose run may be too long for gravity drainage. In that case, a dishwasher drain pump ($30-$50) boosts the water to the disposal or drain connection. Replace the dishwasher drain hose every 8-10 years. The rubber degrades from heat (the dishwasher drains at 130-140°F) and develops cracks that leak slowly onto the cabinet floor.
What tools do I need to connect a dishwasher to a garbage disposal?
You will need: Screwdriver and hammer (to knock out the disposal drain plug on new units), Hose clamp -- worm-gear type ($1-$2), Zip ties (for securing the high loop to the underside of the countertop), Pliers (for removing the knocked-out drain plug from inside the disposal), Dishwasher drain hose ($8-$15, if replacement is needed).
When should I call a professional instead of doing this myself?
You do not need a plumber for this connection. It is a standard part of dishwasher and disposal installation. Call a plumber only if the disposal does not have a dishwasher inlet (very old or commercial models), if you need an air gap device installed on the countertop (requires drilling a hole in the sink or countertop), or if the drain hose run is exceptionally long and needs a drain pump.
How difficult is this project?
This project is rated easy. Most homeowners with basic tools can complete it.
How long does this take?
Plan for approximately 15 - 30 minutes. First-timers may need extra time.
How much will this cost?
The estimated cost is $5 - $15 for hose and clamp. Costs vary by location and materials chosen.