Homeowners often ask how a dishwasher drain hose should be connected during garbage disposal installation with dishwasher connection service. When we replace a disposal under a kitchen sink, we remove the old unit, mount the new disposal to the sink flange, reconnect the drain pipe, and attach the dishwasher drain hose to the inlet port if a hose is already connected to the disposal.
5 Corners Plumbing provides garbage disposal replacement throughout Seattle, King County, and Snohomish County.
Q: Where does the dishwasher drain hose connect to a garbage disposal?
A: The dishwasher drain hose needs to connect to an air gap or a Johnson Tee to meet UPC (Uniform Plumbing Code) requirements. This connection prevents contaminated water from back-siphoning into your dishwasher’s clean water supply.
An air gap mounts on your sink and provides a visible air break in the drain line. A Johnson Tee is installed in the wall behind your dishwasher as part of the drain standpipe; you won’t see it because it’s concealed in the wall cavity.
From the air gap or Johnson Tee, the drain line then connects to the dishwasher inlet port on the side of your garbage disposal. Make sure to remove the factory plug from the inlet before connecting, or your dishwasher won’t drain.
Q: What is the knockout plug inside the inlet port?
A: Many new disposals include a factory knockout plug inside the dishwasher drain inlet port. When the dishwasher drain hose connects to the disposal inlet port, we remove the knockout plug to allow dishwasher water to flow into the disposal body.
During installation, we remove the knockout plug and physically remove the loose plastic piece from inside the disposal chamber before mounting the unit under the sink.
Q: What happens if the knockout plug is left in place?
A: If the knockout plug remains inside the inlet port, the dishwasher drain hose cannot discharge water into the disposal chamber. For that reason, we confirm the inlet port opening is clear before securing the dishwasher hose with the hose clamp.
We visually confirm the inlet port is open and that no plastic obstruction remains inside the disposal body.
Q: Does the disposal need to face a certain direction for the dishwasher hose?
A: Yes, the disposal should be positioned so the dishwasher inlet port faces toward your dishwasher for the easiest hose connection. However, the most important alignment is ensuring the drain outlet on the disposal aligns with your existing plumbing connection under the sink.
We align the disposal during installation so the drain outlet connects properly to your existing drain pipes first. Then we work with the dishwasher inlet orientation from there. In most installations, you’ll have enough flexibility in the dishwasher drain hose to reach the inlet port, even if it’s not in the ideal position.
Q: What parts are handled during garbage disposal replacement?
A: 5 Corners Plumbing replaces garbage disposals; we do not repair them. During replacement, we work with the parts under the sink, including the following:
- The existing disposal unit
- The sink mounting flange
- Plumber’s putty at the mounting flange
- The drain pipe connected to the disposal outlet
- The dishwasher drain hose and hose clamp, when present
- The electrical wiring or the disposal power cord
We remove the existing disposal from the mounting flange. We remove and reinstall the mounting flange using plumber’s putty before attaching the new disposal. After mounting the new unit, we reconnect the drain pipe and, where applicable, re-attach the dishwasher hose to the inlet port.
Q: How do you secure the dishwasher hose properly?
A: After sliding the dishwasher drain hose over the inlet port, we position a hose clamp around the hose and tighten it until the hose sits firmly on the inlet port without slipping. We gently pull on the hose to confirm it remains secure.
Q: How do you test the dishwasher connection after installation?
A: After completing the disposal replacement and dishwasher hose connection, we restore electrical power and turn on the water at the sink faucet. We operate the disposal while water flows into the sink.
We inspect the following areas for leaks:
- The dishwasher hose at the inlet port
- The hose clamp connection
- The drain pipe at the disposal outlet
- The mounting flange area at the sink opening
The installation is complete when the disposal turns on and runs normally, water flows through the drain without backing up into the sink, and no leaks appear under the sink.
Further Reading:
- Curious Reasons a Bathroom Faucet Keeps Dripping Even After It Is Fully Turned Off
- Knowing When a Professional Should Replace a Failing Garbage Disposal Unit
Schedule Your Service
A dishwasher hose must be secured to the disposal inlet port, the knockout plug must be removed, and the hose clamp must be tightened before the unit is operated. During replacement, we remove the existing disposal, reinstall the mounting flange with plumber’s putty, mount the new unit, reconnect the drain pipe, and secure the dishwasher hose when present.
Contact 5 Corners Plumbing today to schedule your garbage disposal installation with a dishwasher connection.