Why is my dishwasher not draining properly?

Why is my dishwasher not draining properly?

There’s nothing more frustrating than a dishwasher that won’t drain properly. It can be a messy and unpleasant experience, not to mention the potential damage it can cause to your appliance and surrounding areas.

If you’re experiencing draining issues with your dishwasher, there could be a number of reasons behind it.

In this article, we’ll explore the most common causes of dishwasher drainage problems and provide expert advice on how to solve them.

Key Takeaways

  • A clogged drain hose is one of the most common causes of a dishwasher not draining properly
  • Air gap blockage can also lead to drainage issues
  • Improper installation can be a root cause of dishwasher drainage problems
  • Dishwasher filter clogs can hinder proper drainage
  • The check valve prevents water from flowing back into the dishwasher

Clogged Drain Hose: The Culprit Behind Your Dishwasher’s Drainage Problems

Is your dishwasher not draining properly? One of the common reasons behind this issue is a clogged drain hose. In this section, we’ll discuss how to identify and clear a blocked drain hose.

A drain hose is responsible for carrying water from the dishwasher to your sink’s drainage system. Over time, this hose can become clogged with food particles, soap residue, and grease, leading to a buildup that prevents water from flowing properly.

To check if your drain hose is blocked, remove the kick plate at the bottom of your dishwasher and locate the hose. Detach the hose from the dishwasher and hold it over a bucket. If water doesn’t flow freely, then it’s likely that the drain hose is clogged.

To clear a blocked drain hose, you’ll need to follow these steps:

  1. Shut off the power to your dishwasher to avoid any accidents.
  2. Detach the drain hose from the dishwasher and the sink’s drainage system.
  3. Carefully dislodge any visible debris from the hose by running a long, thin object through it.
  4. Use a plumbing snake or a wire hanger to remove any stubborn clogs that cannot be easily dislodged.
  5. Reattach the drain hose and test if the water is draining properly.

If the above steps do not resolve the issue, it’s best to call a professional to inspect and identify the root cause of the drainage problem.

By following these steps, you can clear a clogged drain hose and restore proper drainage to your dishwasher.

Garbage Disposal Clog: A Common Cause of Dishwasher Drainage Problems

A garbage disposal unit connected to a dishwasher is an efficient way to dispose of food waste. However, a clog in the disposal unit can lead to drainage issues in your dishwasher.

To determine if a clogged disposal unit is the culprit behind your dishwasher drainage problems, start by:

  1. Running the disposal unit to clear any food scraps trapped inside the unit
  2. Checking the drain to ensure water flows freely down the sink
  3. Running the dishwasher to observe for any improvements in drainage

If the issue persists, you may need to clear the clog. Before attempting to clear the disposal unit, turn off the power or unplug the unit to prevent any accidents.

Steps to Clear a Clogged Garbage Disposal:

1. Insert a hex key into the hole found at the bottom of the disposal unit. Then, wiggle the hex key back and forth until it moves freely.

2. Turn on cold water in the sink and turn on the disposal unit. Listen carefully for any unusual sounds or grinding noises that may indicate the unit is still clogged.

3. If the unit is still clogged, try using a plunger to clear the blockage.

4. If the plunger does not work, remove the P-trap and clear any blockage manually. Remember to place a bucket underneath the P-trap to catch any water and debris.

Once the clog is cleared, run the dishwasher again to confirm that the drainage problem is fixed.

Tip: To prevent future clogs in your garbage disposal, avoid disposing of fats, oils, and greases down the drain. These substances can solidify and clog the unit.

Air Gap Blockage

If you have a dishwasher connected to your sink, it’s likely that you have an air gap installed. The air gap is an essential part of the dishwasher’s drainage system, preventing any dirty water from flowing back into the dishwasher.

In some cases, the air gap can become clogged, leading to drainage problems with your dishwasher. If the dishwasher is not draining correctly and you suspect that the air gap may be the culprit, follow these steps to clean and unclog it:

  1. Locate the air gap device. This is usually located on the sink’s countertop or on the back of the sink.
  2. Remove the chrome cover. Underneath, you’ll see a plastic cap.
  3. Remove the plastic cap and clean it thoroughly.
  4. Insert a straightened paper clip into the air gap’s opening to remove any blockages.
  5. Reassemble the air gap device and run the dishwasher.

By following these steps, you can clear any blockages that may be causing the air gap to malfunction, and ultimately, improve your dishwasher’s drainage performance.

Pump Failure: The Culprit Behind Your Dishwasher Drainage Woes

If your dishwasher is not draining correctly, the pump could be the problem. The dishwasher pump is responsible for removing water from the machine and pushing it out of the drain hose. If the pump fails, water will not drain appropriately, eventually leading to overflow, and even damage to the appliance and your home.

Here are some signs that your dishwasher pump is malfunctioning:

  • Water not draining from the machine properly
  • The pump making a loud, unusual noise during the operation
  • Dishes remaining dirty after a wash cycle

If you notice any of these signs, it’s crucial to address the issue promptly. The good news is that replacing a dishwasher pump is a relatively simple and inexpensive fix compared to other dishwasher parts.

Here is a step-by-step guide to replacing a dishwasher pump:

  1. Remove the bottom rack of the dishwasher.
  2. Locate the dishwasher pump, usually at the base of the machine.
  3. Detach the drain hose from the pump, which may require pliers or a screwdriver.
  4. Unscrew the mounting bracket and lift out the old pump.
  5. Install the new pump, ensuring the mounting bracket and drain hose are appropriately secured.
  6. Reinstall the bottom rack and test the dishwasher for proper drainage.

If replacing the pump seems too complicated or you’re not sure if it’s the problem, consider contacting a professional dishwasher repair service. They can diagnose the issue and recommend the best course of action.

“A faulty pump can lead to improper drainage, and eventually cause water damage to your home. If you suspect your dishwasher pump is malfunctioning, act quickly to prevent further damage.”

Drain Valve Obstruction: A Common Cause of Dishwasher Drainage Problems

If your dishwasher is not draining correctly, a blocked drain valve can be the root cause. The drain valve is responsible for draining the water out of the dishwasher after a cycle is complete. If the valve is obstructed, the water will not drain properly, resulting in drainage problems.

To check if the drain valve is blocked, locate it at the dishwasher’s bottom and remove any debris or foreign object that may be causing the obstruction. After cleaning the valve, run a cycle to see if the drainage issue has been resolved.

Symptoms of a Blocked Drain Valve Steps to Clear the Obstruction
The dishwasher is not draining after a full cycle Locate the drain valve and remove any debris or foreign objects that may be causing the obstruction. After cleaning the valve, run a cycle to see if the drainage issue has been resolved.
The dishwasher is making unusual noises during the cycle Inspect the drain valve for any signs of damage or wear. If the valve is damaged, it may need to be replaced by a professional technician.

If the above steps do not solve the drainage issue, it may be necessary to seek the advice of a professional technician. They can diagnose and fix any underlying problems with the dishwasher, ensuring it is operating at optimal performance.

Improper Installation

Improper installation of a dishwasher can often lead to drainage issues. If the unit is not level or not installed correctly, it can cause water to accumulate in the dishwasher rather than drain out. Here are some common installation issues that can lead to improper drainage:

Installation Issue Solution
Dishwasher not level Adjust the leveling feet to ensure the dishwasher is level from front to back and side to side.
Missing or improper drain loop Ensure that the drain hose is looped up to the underside of the countertop and secured in place. This is known as a high loop installation and prevents water from flowing back into the dishwasher. If the unit is connected to a garbage disposal, an air gap installation is required.
Incorrect drain hose installation Make sure that the drain hose is not kinked or twisted and is connected tightly to the dishwasher and drain or garbage disposal. A loose or improper connection can cause leakage and drainage issues.

It’s important to follow the manufacturer’s installation instructions carefully to avoid any installation issues. If you’re unsure about the installation process, it’s best to seek the help of a professional to ensure that the unit is properly installed.

dishwasher installation

High Loop or Air Gap Installation

One common reason for dishwasher drainage problems is an improperly installed drain hose. The drain hose must be installed in a high loop or an air gap to prevent wastewater from flowing back into the dishwasher.

In a high loop installation, the hose is attached to the underside of the countertop or sink and then loops up above the level of the dishwasher before connecting to the sink drain or garbage disposal. An air gap installation involves a device that is mounted on the sink or countertop, separate from the dishwasher, and creates a gap between the dishwasher and sink drain.

Without a high loop or air gap installation, wastewater can easily flow back into the dishwasher, causing drainage issues. It’s important to ensure that the installation is done correctly to prevent this problem from occurring.

If you’re unsure whether your dishwasher is installed with a high loop or air gap, consult the manufacturer’s installation guide or a plumbing professional for assistance.

Why is a High Loop or Air Gap Installation Important?

A high loop or air gap installation is crucial as it creates a physical barrier that prevents wastewater from flowing back into the dishwasher. Without this barrier, there’s a risk of dirty water and food particles entering the dishwasher, causing clogs and drainage issues.

In addition, some local plumbing codes may require a high loop or air gap installation to ensure compliance with sanitation and safety regulations.

By having a high loop or air gap installation, you can ensure that your dishwasher drains properly, preventing any potential safety hazards and prolonging the lifespan of your appliance.

Dishwasher Filter Clog

If your dishwasher is not draining properly, a clogged filter could be the culprit. Over time, food particles and debris can accumulate in the filter and block the water from draining out of the dishwasher.

To locate and clean the filter:

  1. Remove the bottom dish rack from the dishwasher.
  2. Locate the filter at the bottom of the dishwasher. It may be circular or rectangular in shape.
  3. Remove the filter and rinse it under hot, running water to remove any debris or food particles.
  4. Inspect the filter for any damage or cracks. If the filter is damaged, it will need to be replaced.
  5. Reinstall the filter back into the dishwasher and replace the bottom dish rack.

Regularly cleaning the dishwasher filter can help prevent drainage problems and ensure your dishwasher is running efficiently.

Faulty Check Valve

If your dishwasher is still not draining correctly, the issue could be a faulty check valve. The check valve stops water from flowing back into the dishwasher and is located in-line with the drain hose or in the dishwasher’s pump housing.

To diagnose a faulty check valve, you can follow these steps:

  1. Remove the drain hose from the dishwasher and place it over a bucket or sink. Run the dishwasher’s drain cycle and check if water flows through the hose.
  2. If water does not flow, remove the check valve and inspect it for any visible damage or blockages.
  3. If the check valve appears damaged or is blocked, it will need to be replaced. You can purchase a new check valve from a local appliance store or online.
  4. Install the new check valve and reattach the drain hose before running the dishwasher to test the drainage.

If replacing the check valve does not solve the problem, there could be an issue with the dishwasher’s pump or drain valve. It’s best to contact a professional technician to diagnose and fix the problem.

Faulty Check Valve

Note: Always remember to disconnect the dishwasher from the power source before attempting any repairs.


Dealing with a dishwasher that isn’t draining properly can be frustrating, but don’t worry, you’re not alone. We’ve covered some of the most common reasons behind dishwasher drainage problems and how to fix them.

Remember to always check and clear a clogged drain hose, garbage disposal unit, and air gap as these are the most frequent culprits of improper drainage. It’s also essential to inspect and clear any obstructions in the drain valve and check for faulty check valves.

If you’re unsure of how to perform any of the fixes discussed in this guide, it’s always best to call a professional. Improper installation and handling of the dishwasher can lead to more significant issues.

By following the steps provided in this comprehensive guide, you too can solve your dishwasher drainage issues and get your appliance back to optimal performance.

Max Appliance Repair

Written by Max | An appliance repair technician with more than 15 years experience in appliance repair services in Toronto and the GTA.

Disclaimer: This post "Why is my dishwasher not draining properly?" is for information purposes only. If you need specific help, please contact Max Appliance Repair at https://maxfix.ca/contact/.