Introduction
Having a dishwasher that won’t drain properly can be a major inconvenience. Dirty water left sitting in the dishwasher tub can lead to foul odors, leaks, and growth of bacteria and mold. Fortunately, there are a number of ways to troubleshoot and fix a dishwasher drainage problem yourself without having to call an expensive appliance repair technician.
This comprehensive guide will provide you with step-by-step instructions for diagnosing and repairing a dishwasher that won’t drain. We’ll cover the most common causes of dishwasher drainage problems and show you how to check and fix clogged pumps, hoses, valves, filters, and more. With a little bit of effort, you can get your dishwasher draining properly again and avoid the hassle and expense of replacement.
What Causes a Dishwasher to Not Drain Properly?
Before you can fix a dishwasher that won’t drain, it’s important to understand what causes drainage problems in the first place. Here are some of the most common culprits:
Clogged or Malfunctioning Drain Pump
The drain pump is responsible for pumping water out of the dishwasher tub and into the drainage system. A clog in the pump or a pump failure can prevent proper water removal. Food particles, grease, soap scum, and other debris can all get lodged in the drain pump impeller blades and jam the pump.
Clogged Drain Hose/Garbage Disposal
If your dishwasher drain hose connects to the garbage disposal, a clog in the hose or disposal can block drainage. Food debris and grease are the most common causes of clogged hoses and disposals. Kinked hoses can also impede proper water flow.
Faulty or Stuck Drain Valve
At the bottom of the dishwasher tub is a drain valve that opens to allow water to exit into the drain pump and hose. If this valve fails to open fully or becomes stuck shut, drainage will be impaired. Debris, mineral deposits, and corrosion can all cause the valve to malfunction.
Clogged Air Gap
Some dishwashers have an air gap installed on the drain hose near the sink. This vent prevents backflow of dirty water but can become clogged with food particles or debris. A blocked air gap restricts proper water drainage.
Obstructed Sink Drain Line
If the dishwasher drain hose connects directly to the sink drain line, a clog in the sink drain itself can back up water into the dishwasher tub and prevent drainage. Grease, soap scum, hair, and other gunk in the drain line are often the culprits.
Clogged Filter
Dishwashers have filters to trap food particles, grease, and other debris coming off the dishes. Over time these filters can become clogged and blocked, impeding water from properly draining out of the tub.
Now that you know what causes dishwasher drainage problems, let’s go through the steps to diagnose and fix a unit that won’t drain.
How to Fix a Dishwasher That Won’t Drain
Follow these troubleshooting tips to get your dishwasher draining properly again:
1. Turn off power and water supply
Before doing any work on your dishwasher, make sure to turn off the power supply to avoid electrocution. Turn off the water supply as well so water does not spray out when you detach hoses or remove parts.
2. Remove standing water
Open the dishwasher door and use a sponge to soak up excess water sitting in the bottom of the tub. Place towels under the unit to catch any leaks. The tub should be as dry as possible to facilitate repairs.
3. Check drain hose and garbage disposal
Check where the drain hose connects, either to the garbage disposal or sink drain pipe. Make sure there are no kinks or blockages in the hose. Fill the sink with water to check for proper drainage. If water does not drain from the sink, the garbage disposal or drain line may be clogged and require cleaning.
4. Clean air gap, if present
Pull out the air gap assembly and inspect it for obstructions. Use a toothpick or pipe cleaner to clear out any debris or food particles clogging the vent opening. Reinstall the air gap once it is clean and clear of obstructions.
5. Clean sink drain line and garbage disposal
If you have a garbage disposal, turn it on to check for obstructions and clean it thoroughly. You can use a screwdriver or hex wrench inserted in the center hole to turn the disposal blades by hand and dislodge debris. For stubborn clogs, you may need to disconnect the disposal and snake the drain line from below. Alternatively, use a chemical drain cleaner to dissolve grease and clear the line.
6. Check and clean drain filter
Your dishwasher filter prevents food particles from getting into the drain pump. Over time it can become clogged and restrict water drainage. To clean it, remove the filter housing located along the bottom of the tub. Rinse the filter under hot water to remove debris and then replace it.
7. Test and clean drain valve/anti-siphon
The drain valve (also called an anti-siphon) is located under the filter housing. Remove the valve and inspect it for obstructions or debris. Use a toothbrush and water to scrub and clean the valve if dirty. Make sure the valve pieces move freely when reassembled. The spring-loaded seal should move up and down smoothly and close tightly.
8. Disassemble and clean drain pump
If cleaning the filters, hoses and valves hasn’t resolved the drainage problem, the drain pump itself will need to be inspected and cleaned. First turn off power and water supply to the dishwasher. Then remove the lower access panel to expose the pump. Disconnect the hoses, remove any mounting fasteners and take out the pump. Clean out any debris from the impeller and cavity. Make sure the impeller turns freely after reassembly.
9. Test cycle and confirm proper drainage
With all the drains cleared and parts reassembled, run an empty wash cycle and verify that water pumps out completely. Let the dishwasher run until the end of the cycle to ensure proper drainage. You want to see no water left standing in the tub once finished.
10. If problem persists, replace pump or valve kit
If cleaning the existing drain pump, hoses and valves fails to resolve the drainage issues, the parts may need replacement. You can purchase dishwasher drain pump or drain valve repair kits from appliance parts retailers online and install them yourself. Just be sure to get the proper replacement kit for your dishwasher make and model. Watch online videos for step-by-step installation guides.
Dishwasher Drainage FAQs
Below are answers to some of the most frequently asked questions about fixing dishwashers that won’t drain:
Q: Why does my dishwasher have standing water in the bottom?
A: Standing water is usually caused by a blockage in the drain path—the most common causes are a clogged drain hose, faulty drain valve, or malfunctioning drain pump. Check and clean these components.
Q: Why would my dishwasher not be draining at all?
A: If your dishwasher fails to drain at all, the most likely cause is a drain pump failure or a completely blocked drain hose/valve. You’ll need to clear any obstructions or replace the defective pump.
Q: What should I do if my dishwasher is slowly draining?
A: Slow draining means there is a partial blockage in the drain system. Check the drain hose for kinks or food clogs. Remove and clean the drain filter, air gap, drain valve, and drain pump as needed.
Q: What causes the foul odors coming from my dishwasher?
A: Standing water that hasn’t drained fully allows mold and bacteria to grow inside the tub, causing unpleasant odors. Fix any drainage issues and use dishwasher cleaners regularly.
Q: Why is dirty water pooling around my dishwasher?
A: Leaks around the tub are usually caused by a faulty drain hose or seal. Inspect the hose connections and replace any worn or damaged seals/gaskets on the tub.
Q: Should I use a drain cleaner to unclog my dishwasher?
A: Chemical drain cleaners are too harsh for a dishwasher and can damage the plastic and rubber components. Use a Zip-It tool, long flexible auger or disassemble parts to remove drain clogs manually.
Q: My dishwasher won’t drain and is making a humming noise—what’s wrong?
A: A humming or buzzing sound usually indicates an issue with the drain pump motor. Try cleaning the pump, but you may need to replace the entire pump assembly if that doesn’t work.
Q: How can I remove and clean the drain pump on my dishwasher?
A: Turn off power/water, disconnect hoses and remove access panels. Remove any pump mounting fasteners, disconnect wiring, and pull out the assembly. Rinse and clean the housing, impeller and inlet covers. Reinstall the cleaned pump.
Q: What tools do I need to work on my dishwasher drain?
A: Basic tools like screwdrivers, pliers, a turkey baster, towels, flashlight and bucket are handy for dishwasher drain repairs. Specialty items like a Zip-It tool or drain auger may be necessary for tough clogs.
Preventing Future Dishwasher Drain Problems
To avoid recurring drainage failures, here are some tips to keep your dishwasher draining smoothly:
- Clean the filter monthly to prevent debris buildup
- Use a dishwasher cleaner monthly to dissolve grease and limescale
- Don’t wash excessively greasy or dirty dishes which can clog drains
- Run an empty wash cycle with vinegar to keep drains clear
- Don’t place dishes or utensils in front of the detergent cup
- Periodically inspect the drain hose and pumps for obstructions
- Always scrape food scraps off dishes before washing
- Ensure the kitchen sink garbage disposal is clear and draining well
- Don’t overload the dishwasher or allow debris to accumulate in the tub bottom
Following these preventive measures along with regular drain cleaning and maintenance will keep your dishwasher draining properly for years to come. Act quickly when you notice any signs of drainage problems to avoid permanent damage.
When to Call a Repair Professional
While many common dishwasher drainage problems can be fixed yourself, there are times when it’s best to call in a professional:
- If you can’t find the source of the clog after thoroughly checking the drain system
- For complex repairs like dishwasher tub replacement or control board issues
- If the dishwasher drain leaked and caused water damage
- If the drain pump needs replacement and you don’t feel comfortable doing it
- For installation of a new dishwasher drain hose or garbage disposal
- If repair efforts have failed and you need an expert diagnosis
Many appliance repair shops offer reasonable rates for servicing dishwashers. They have specialized tools and knowledge to efficiently troubleshoot tricky drainage problems. Consider calling for professional assistance if your DIY efforts don’t get your dishwasher draining again.
Conclusion
A dishwasher that fails to drain is a headache, but one that can often be fixed with some targeted troubleshooting and repair. In most cases, the problem is caused by a clogged drain hose, pump, garbage disposal or valve. By methodically checking each component and cleaning or replacing clogged parts, you can get your dishwasher draining properly again without waiting days for a service appointment.
Regular cleaning of the filters, pumps and drain lines is also crucial for preventing future drainage problems. Keep this guide handy so you can refer to the step-by-step instructions when needed. With a few basic tools and supplies, a little patience and some elbow grease, you can tackle most dishwasher drainage failures yourself. However, don’t hesitate to call in a professional if you can’t resolve the issue on your own.