why would a dishwasher not drain after replacing garbage disposal

A dishwasher that fails to drain correctly is tricky to diagnose because there are lots of possible reasons for the problem, and some dont even involve the dishwasher. Sometimes, it involves issues with the plumbing itself that need to be addressed before you turn to repairing or replacing the dishwasher.

Before you begin troubleshooting, remember that it is normal for some dishwashers to retain a small amount of water at the bottom of the tub after a complete cycle. If you have just a small pool in your machine, check the owners manual (or call the manufacturer) to see if this is normal.

Failing to remove the knockout plug can cause problems between the dishwasher and the disposal. All new garbage disposals have a knockout plug. This plug restricts the flow of water between the disposal and the dishwasher.

How to Diagnose Appliance-Related Causes

If there are no obvious plumbing-related causes, drainage problems may originate with several possible components on the appliance itself.

• Check the Drain Screen

  Check the drain screen at the bottom of the dishwasher tub and make sure nothing is clogging it. Clear plastic lids, glass, labels, and bits of plastic can cover the drain, and they can be hard to see unless you look closely. The Spruce / Kevin Norris

• Clean the Filter

  Dishwashers use a variety of filter designs. Some have a simple screen, some have removable filters below the screen, and some require removing the bottom spray arm for a thorough cleaning. Check the appliance manual for instructions on how yours should be cleaned. The Spruce / Kevin Norris

• Check the Dishwasher Drain Hose

  This is usually a corrugated plastic tube that runs from the bottom of the dishwasher to the air gap, garbage disposal, or sink drain, depending on the setup. Turn off the power to the dishwasher by pulling out its plug or switching off the breaker to the dishwasher circuit. Remove the toe-kick panel, then loosen the hose clamp securing the drain hose to the dishwasher pump (have a sponge handy for any water that spills out). Clean the end of the hose, then blow into it. If the hose is plugged and you cant blow through it, remove the clamp on the other end of the hose, then clean the hose out in a sink. If you cant unclog the hose, or if it is old and cracked, replace it.

  Watch Now: How to Replace a Dishwasher Drain Hose

  The Spruce / Kevin Norris

• Replace the Dishwasher

  Appliance repair specialists can be expensive, and if your dishwasher is more than nine or 10 years old and none of the obvious fixes remedies the drainage problem, it may be time to replace the dishwasher. This is not as hard as it sounds, and many homeowners do this work themselves. Some appliance stores will install the dishwasher free of charge as part of the purchase price and they may even handle the disposal of the old appliance. The Spruce / Kevin Norris

How to Diagnose Plumbing-Related Causes

Surprisingly often, drain problems with a dishwasher originate in drain parts outside the appliance itself. Not all the following steps will need to be completed. Continue until you determine the cause of the dishwashers drainage problems. If none of these plumbing-related issues seem to be at fault, then proceed to the diagnosing issues with the dishwasher itself.

• Check the Garbage Disposal

  In most cases, the dishwasher drain hose connects to the disposal. When there is food built up inside the disposal or when the disposal is clogged, there is less space for the dishwasher water to flow. Run the disposer thoroughly with plenty of water running to clear it out. This may fix the drainage problem with the dishwasher. The Spruce / Kevin Norris

• Clean the Air Gap

  This is the small (usually chrome) cylinder on the back edge of the kitchen sink. It prevents air vacuums from forming and thus prevents drain water from siphoning back into the dishwasher. If water comes out of the air gap when you run the dishwasher (and sometimes that water winds up all over the counter), the blockage is between the air gap and the garbage disposer. To clear it, remove the air gap cap and clean the inside the air gap. Next, disconnect the hose that runs from the nipple on the bottom of the air gap to the garbage disposal or the sink drain, and make sure that it is not clogged. The Spruce / Kevin Norris

• Check the High-Loop

  If your dishwasher doesnt have an air gap, its drain hose may be looped up and attached to the bottom of the countertop near the sink. Although this is not code-compliant in most places, it serves the same purpose as the air gap—to prevent drain water from siphoning back into the dishwasher. If this hose has come loose so it is no longer looped up higher than the level of the dishwasher, it may prevent water from properly draining out of the appliance. Returning the hose to its proper high-loop position will fix the problem; or, you can install a proper air gap.

  Tip

  If youve just installed a new garbage disposal, make sure the plug inside the drain hose nipple has been knocked out. New disposals have a little plastic disc covering the drain opening, which must be punched out with a hammer and screwdriver; unless you do, the dishwasher cannot drain into the disposal. The disc falls into the disposers grinding chamber, where you can fish it out. The Spruce / Kevin Norris

Dishwasher not draining after installing new garbage disposal?

FAQ

Can garbage disposal cause dishwasher to not drain?

Does changing garbage disposal affect dishwasher?

Why is dishwasher not draining but no blockage?

Why is my garbage disposal not draining?

Pro tip: If you just installed a new garbage disposal before the dishwasher drain problem occurred, the cause may be a plastic plug inside the tube that connects to the dishwasher drain. To remove this plug, put your flat-head screwdriver in the disposal’s drain tube pipe and hit the back of the screwdriver with a hammer.

How do you stop a dishwasher from draining?

Run your garbage disposal. The drain hose from your dishwasher empties into the garbage disposal drain. If the disposal unit contains unground food, or food sludge has settled in the drainpipe below the disposal, it can prevent even the best dishwasher from draining properly.

How do I troubleshoot a dishwasher that is not draining?

The first step in troubleshooting a dishwasher that’s not draining is pinpointing the type of drain connection beneath the sink. Open the cabinet and look at the configuration of the corrugated dishwasher drain hose and how it connects to the sink drain. The following drain connections are the most common.

Can a dishwasher back up if the drain hose shifts?

Out-of-Position High Loop A dishwasher can back up if the drain hose shifts or gets knocked out of position in a high loop to disposal or high loop to drain kitchen configuration. A high loop system uses gravity to prevent wastewater from draining back into the dishwasher.