Why Does My Sink Fill Up When I Use the Dishwasher?

Your sink filling up with water while your dishwasher is running can be a perplexing situation that might send some homeowners into a panic. Fortunately, this issue is not uncommon and can often be resolved with a bit of troubleshooting.

Common Causes & Solutions

If your sink fills up with water when you try to use your dishwasher, there may be several possible causes. Here are some of the most common reasons why this happens, and some troubleshooting tips you can follow:

Drain Clogs

Problem: A drain clog is one of the leading culprits of a sink filling up while the dishwasher is running. Over time, debris, food particles, and grease can accumulate in the sink and dishwasher drains, restricting water flow. As the dishwasher pumps out water, the clog can cause a backup, resulting in water filling the sink.

Solution: Start by using a plunger to attempt to dislodge the clog. If that doesn’t work, try a drain snake or a mixture of baking soda and vinegar to break down the blockage. Regularly cleaning the sink and dishwasher drains can help prevent future clogs.

Air Gaps

Problem: An air gap is a device that prevents wastewater from flowing back into the dishwasher. If the air gap becomes blocked or is improperly installed, it can lead to drainage problems. When this happens, water from the dishwasher might flow back into the sink.

Solution: Check the air gap for any obstructions and ensure it’s properly connected. Clean the air gap periodically to prevent buildup that can hinder proper drainage.

Disposal Interference

Problem: In some setups, the dishwasher drain hose is connected to the garbage disposal. If the garbage disposal is clogged or not functioning correctly, it can keep the dishwasher from draining effectively, resulting in water backup in the sink.

Solution: Clear any clogs in the garbage disposal and make sure it’s in proper working condition. If needed, consult the manufacturer’s instructions or a professional for help.

Drain Loop

Problem: An improper sink drain loop setup can cause a backflow of water from the dishwasher to the sink. If the drain hose is too low under the sink or doesn’t have the correct loop height, gravity can cause water to flow back into the sink.

Solution: Adjust the drain hose loop according to the dishwasher manufacturer’s instructions. This will create a higher point in the hose, preventing water from flowing backward.

Vent Issues

Problem: Every plumbing system requires proper ventilation to ensure smooth drainage. If the plumbing vents are clogged or obstructed, it can create negative pressure in the pipes, leading to drainage problems.

Solution: If you suspect a plumbing vent issue, it’s best to consult a professional plumber. They can identify and resolve ventilation problems, ensuring proper drainage throughout your plumbing system.

When To Contact a Plumbing Professional

A sink filling with water while the dishwasher is running can be caused by several factors, ranging from simple clogs to more complex plumbing problems. By identifying the root cause and following the appropriate troubleshooting tips, you can restore proper drainage and prevent this inconvenience.

However, DIY troubleshooting techniques might not be enough to resolve the problem in some cases. If you’ve attempted the above solutions to no avail or don’t feel comfortable trying to fix the problem yourself, James A. Wheat & Sons is here to help.

Our plumbing experts offer same-day service availability for all your urgent service requests.

Schedule plumbing repairs with our team by calling (301) 241-9636 today.