Why Does the Sink Fill Up with Water When I Run My Dishwasher?

While it is not the worst plumbing problem you could experience, finding your sink filled with water from the dishwasher is certainly an unpleasant and inconvenient experience. Often times this sort of reoccurring problem can be fixed and prevented with simple cleaning and occasional maintenance. Here is all you need to know to fix and prevent your sink from filling up with water when you run your dishwasher.

Sink and Dishwasher Maintenance 101

Before you attempt to clean or fix your current plumbing problems, be sure to unplug your appliances (dishwasher, garbage disposal, etc.) from their power supply to minimize the risk of electric shock and injury. Turn both the cold and hot water supply valves off to prevent any water flow to your appliances.

It is also important to know that the running water in both your kitchen sink and dishwasher flow out through the same drainage line. So any clog or blockage within that main drainage line can cause water to backup and overflow into your kitchen sink. These clogs typically occur in four places: the dishwasher, the garbage disposal, the sink, and the air gap. Clogs in any of these four locations within your plumbing system can result in water filling your sink when you run your dishwasher.

Obstructed Dishwasher

In general, a little bit of water in the bottom of your dishwasher is normal and nothing to be concerned about. However, if standing water is covering the bottom of your dishwasher it is clearly not draining correctly. You should then check to see if anything is covering or obstructing the drain in the rear of your dishwasher. You may also want to check the drain hose on your dishwasher as they are known to kink and cause blockages. Additionally, be sure you are using the correct brand and amount of detergent for your dishwasher as it can eventually buildup and result in a clog.

Jammed Garbage Disposal

Another potential cause is the drain plug on your garbage disposal. The drain plug covers the hole where the garbage disposal is connected to your dishwasher and if left on the garbage disposal it can result in water not properly draining from your dishwasher or sink. This problem generally occurs when a new garbage disposal is recently installed. Simple remove the drain plug from the garbage disposal to resolve this problem.

Clogged Sink

It is possible that you may have a clog in your sink that is preventing water from your dishwasher to drain properly. You can attempt to resolve this issue in three ways:

1. Run the Garbage Disposal
   It is always recommended that you run your garbage disposal for a couple of seconds before starting your dishwasher to ensure that no food or debris is preventing the proper drainage of water from your dishwasher.
2. Use Sink Cleaners
   To help clear a clog within your sink drain, purchase and use brand name sink cleaners to help breakup any clogs or bacteria buildup.
3. Snake the Drain
   If your garbage disposal or sink cleaners cannot handle the job, you can attempt to clear the drain by purchasing a sink snake from your local hardware store.

If none of these solutions unclog your sink it is recommended that you contact a local plumber to resolve the issue.

Blocked Air Gap

Finally, if you have an air gap installed with your kitchen sink it is possible that the air gap is clogged, preventing your dishwasher from draining and resulting in a full sink of water. The air gap can be found on the top of the sink usually next to your faucet and is used as a backflow prevention device for your dishwasher. If water is flowing from your air gap device there is most likely a clog within the device that needs attending to. To clean and maintain your air gap device, simple remove the top cover and then unscrew or unsnap the inner protective cap to look inside your air gap device. From here, sometimes the debris is visible and easy to remove while other times a more serious blockage may require the use of a twelve inch bottle brush that you can purchase at any local home improvement or hardware store. Use the bottle brush to clean and clear your air gap device of any debris.

As an overall maintenance tip for your kitchen plumbing and appliances, do not treat your garbage disposal and sink like a trash can. Knowing what not to put down your sink (bones, rice, pasta, potato peals, etc.) will help prevent clogs from ever occurring.

Following these repair and maintenance instructions will help ensure you don’t have to deal with messy clogs, unwanted inconveniences, and a dishwasher that overflows into your sink.