A residential dishwasher drain hose carries wastewater from the dishwasher’s drain pump to the household drainage system. Its route matters: sharp bends restrict flow, while an incorrectly arranged drain connection can let wastewater from the sink drain flow back into the dishwasher.
To assess the setup, follow the hose’s path, check its backflow protection and connections, and use the dishwasher’s installation instructions alongside local plumbing requirements.
High loop or air gap: what the routing needs to accomplish
Whirlpool’s drain-loop guidance calls for the hose to rise before descending to its drain connection, using a secured high loop or a deck-mounted air gap. These arrangements help prevent wastewater from being siphoned back into the dishwasher.
High loop
A high loop is an elevated section of drain hose secured near the underside of the countertop. The hose should rise to that secured point without a low sag between the dishwasher and the top of the loop, then descend to the drain connection. A loose loop that falls out of position does not maintain the intended routing.
Air gap
An air gap is a small, dome-shaped fitting mounted on the sink deck or countertop. The dishwasher hose connects to its inlet, and a separate short hose carries discharge from its outlet to the sink drain. Its air vent equalizes pressure to help prevent backflow.
Choose the arrangement required for your installation, not simply the one that fits most easily. In the US, local plumbing rules determine whether a high loop is accepted or a deck-mounted air gap is required. Use a high loop only where both the dishwasher manufacturer and local code allow it; the local plumbing authority makes the final determination.
How to check the drain hose’s path
Before inspecting or disconnecting the hose, shut off the water supply valve under the sink and disconnect the dishwasher’s power. Unplug a plug-connected unit or switch off its circuit at the breaker panel; use the breaker for a hardwired dishwasher.
- Identify where the hose ends. A typical under-sink connection is a wye branch on the sink drain tailpiece when there is no garbage disposal, or the disposal’s dedicated dishwasher inlet when one is present. Another permitted arrangement under the 2021 International Residential Code uses an air break to a standpipe.
- Check the required rise and support. Confirm that the backflow-protection arrangement described above is securely installed. Follow the model’s instructions for routing height, total hose run, support, and any permitted extension. Do not use another dishwasher model’s limits to plan yours.
- Look along the full accessible run. Whirlpool recommends a direct path to the sink drain or disposal, without pinches, kinks, or sharp bends that obstruct water flow. Check that the hose has not been folded or left with a low sag.
- Check the connections. Clamps should secure both ends, and each connection should be firmly seated on the correct inlet. Use the hose type specified for the dishwasher rather than substituting one based only on fit.
Symptoms that point you toward the hose—and other causes to check
Standing water at the bottom of the tub after a cycle, gurgling, and water backing up into the sink are reasons to check the drain hose for kinks, clogs, or incorrect routing. These symptoms do not identify the hose as the cause by themselves.
- A visible pinch or sharp bend: This restricts flow and is a specific routing problem to address.
- Wastewater returning to the dishwasher: Check whether the high loop or air gap is correctly arranged rather than treating the problem only as a blockage.
- Poor drainage with no obvious hose problem: Include a clogged dishwasher filter and a blocked garbage disposal in the diagnosis.
- No drainage immediately after a new disposal connection: Have the installer verify that the factory knockout plug was removed from the disposal’s dishwasher inlet before the hose was connected. A plug left in place blocks drainage even when the hose itself is sound.
When installation calls for a plumber or service technician
Before arranging installation, confirm the applicable local plumbing requirements with the authority having jurisdiction, including whether the work requires a licensed plumber. Resolve those requirements before changing the hose route.
Use a qualified service technician or installer when the dishwasher’s installation manual requires one. Bosch installation instructions call for a qualified service technician or installer, and the Kenmore/Electrolux installation manual calls for a qualified service technician. Both require compliance with national and local electrical and plumbing codes.
Drain hookup is part of appliance installation, not just hose placement. GE’s instructions identify mechanical, electrical, and plumbing skills as necessary for installation and place responsibility for proper installation on the installer.