The Empathy Hook & Rapid Diagnosis: The Swampy Surprise

You run a full load of dishes after dinner, open the dishwasher door the next morning expecting sparkling clean plates, and instead, you are hit with a foul odor. Looking down, you see a murky puddle of gray, food-filled water pooling at the bottom of the tub.

It is incredibly frustrating, and it completely defeats the purpose of the appliance. But before you panic and assume you need to buy a brand new $800 dishwasher, know that a draining failure is rarely a death sentence for the machine. In most cases, the dishwasher is trying to pump the water out, but the plumbing is blocking its path.

If your dishwasher won't drain, it is almost always caused by one of these four blockages:

A Clogged Filter Basket: The plastic filter at the bottom of the tub is completely choked with food debris, labels from jars, or broken glass.
A Garbage Disposal Issue: A heavy clog in the disposal, or a newly installed disposal that still has its factory "knockout plug" intact.
A Blocked Air Gap: The small silver cylinder sitting next to your sink faucet is jammed with food particles.
A Kinked Drain Hose: The plastic corrugated tube running behind or under the dishwasher was crushed when the unit was pushed back into the cabinet.

The "DIY Check" Section: Be Your Own Appliance Tech

Dishwasher drainage issues are one of the most common plumbing calls, but 50% of the time, homeowners can fix it themselves in under five minutes. Run through these safe, simple checks before you pick up the phone.

1. Clear the Dishwasher Filter

At the very bottom of the dishwasher tub, below the lower spray arm, sits a cylindrical filter basket. Twist it counter-clockwise and pull it out. Take it to the sink and scrub away the grease, food sludge, and calcified soap scum with an old toothbrush. Reinstall it and press the "Drain/Cancel" button on your dishwasher panel to see if the water finally drops.

2. Run (and Clear) the Garbage Disposal

Because the dishwasher drain hose typically connects directly into the side of the garbage disposal, a clog in the disposal means a clog for the dishwasher. Run the hot water and turn on the disposal for 15 seconds to clear out any heavy food waste.

Pro Tip for New Installs: If you just installed a brand-new garbage disposal yesterday and the dishwasher won't drain today, the installer forgot to punch out the "knockout plug"—a solid piece of plastic inside the disposal’s inlet port that literally blocks the water from entering.

3. Clean the Air Gap

If you have a small cylindrical dome sitting next to your sink faucet (an air gap), it is designed to prevent dirty sink water from siphoning back into your clean dishwasher. If water is shooting out of this little dome onto your counters, the hose between the air gap and the disposal is clogged. Pop off the silver cover, remove any gunk with a pair of tweezers or a bottle brush, and test the drain again.

The Pivot: When to Call a Licensed Professional

If you have cleaned the filters, cleared the disposal, and checked the hoses but the water still won't budge, you have likely crossed from a simple appliance maintenance task into a deeper plumbing failure or an electrical breakdown.

You must call a professional if you experience any of the following:

The Kitchen Sink is Also Backed Up: If your sink is holding standing water right alongside your dishwasher, you don't have an appliance issue—you have a main kitchen line clog. You need a licensed plumber to perform professional drain cleaning using a motorized snake to clear the branch line inside your wall.
Water is Leaking Under the Cabinets: If you see water seeping out from underneath the toe-kick of your cabinets, the dishwasher pump seal has likely failed, or the drain hose has snapped. Shut off the water supply immediately to prevent rotting your subfloor.
The Pump Motor is Dead or Humming: If you press the "Drain" button and hear a loud buzzing noise (or absolutely nothing at all), the dishwasher's drain pump motor has likely seized or burned out.

If the problem is tied to a jammed or failing disposal unit, review our guide on garbage disposal repair costs to see if it makes more financial sense to fix the old unit or upgrade to a more powerful model. For deep pipe clogs, check out our national drain cleaning cost guide.

Don't resort to washing dishes by hand for the next month, and definitely don't let standing water ruin your kitchen floors.

Enter your zip code in the True Plumber National Directory today to instantly connect with vetted, licensed plumbers who can clear your lines and get your kitchen running smoothly again.

FAQs

Q: Should there be a little bit of water left at the bottom of the dishwasher?

A: Yes. It is completely normal to have about a half-inch of clean water sitting in the basin directly below the filter basket. This small amount of water is intentionally left behind to keep the rubber pump seals from drying out, cracking, and causing a leak.

Q: Can I pour Drano or liquid plumber into my dishwasher to unclog it?

A: Absolutely not. Chemical drain cleaners are highly corrosive and generate extreme heat. Pouring them into a dishwasher will melt the plastic tub, destroy the rubber hoses, and ruin the pump seals. Furthermore, if you open the door mid-cycle, you risk splashing toxic chemicals into your eyes.

Q: Who should I call for this: a plumber or an appliance repairman?

A: It depends on the root cause. If your kitchen sink is draining perfectly fine, but the dishwasher motor is totally dead and won't pump, call an appliance repair technician. If the kitchen sink is also backing up, or if the garbage disposal is jammed and leaking, call a licensed plumber.