Thermador Dishwasher Not Draining? Here’s Why

Thermador produces high-end, heavy-duty dishwashers known for their excellent cleaning and drying performance. If your Thermador dishwasher is currently experiencing a drainage issue, you’ll want to get it fixed as soon as possible so you can keep enjoying all of the benefits this premium appliance offers.

Fortunately, most drainage problems with Thermador dishwashers are fixable, though some may require more effort than others. This article will cover the most likely reasons your Thermador dishwasher isn’t draining and offer tips for resolving these issues.

Why your Thermador dishwasher isn’t draining

Here are the five most common causes of a Thermador dishwasher not draining properly.

1. The filter needs cleaning

The filter in your Thermador dishwasher needs to be cleaned regularly so it doesn’t become clogged, especially after washing dishes with a lot of food residue. A clogged filter can result in a dishwasher that won’t drain properly.

Cleaning the filter is a simple task. Follow these steps to do so:

1. Unplug the dishwasher.
2. Open the dishwasher door and remove the lower rack.
3. Locate the filter at the base of the tub.
4. Unscrew the filter, turning it counterclockwise, then lifting it out.
5. Disassemble the filter then rinse each of its parts under running water. Use a soft brush if the filter is heavily soiled.
6. Reassemble the filter and place it back inside the dishwasher.

2. The drain pump impeller is blocked

The drain pump has an impeller, which spins and pushes the wastewater out of the dishwasher during a wash cycle. This small, fan-like component can sometimes get blocked by food particles, small pieces of broken dishware, or other debris, meaning it can’t spin and the water won’t drain.

You can access the impeller without disassembling your appliance since it sits under the pump cover in the filter housing. Follow these steps to check the impeller:

1. Unplug the dishwasher.
2. Remove the lower rack.
3. Remove any standing water with a sponge or small container.
4. Take out the filter.
5. Remove the pump cover from the filter housing. It has a small plastic tab that you can pull on to remove it.
6. Beneath the pump cover, you’ll find the impeller.
7. Check the impeller for any debris or objects that could be blocking its movement. Remove any you find.
8. Manually rotate the impeller to inspect each of its blades. If any are damaged, the drain pump will need to be replaced since you can’t purchase the impeller as a separate part.

3. The drain hose is blocked

Restrictions in the flow of water through the drain hose can occur due to clogs or kinks in the line. A blocked drain hose is one of the most common causes of drainage issues.

Follow these steps to check the drain hose for issues:

1. Turn off the power and water supply to your Thermador dishwasher.
2. Remove the top and bottom racks from the dishwasher.
3. Remove any screws securing the dishwasher to the cabinet or countertop.
4. Disconnect the drain hose from the air gap, garbage disposal, or sink drain.
5. Pull the dishwasher out from under the counter.
6. Disconnect the drain hose from the dishwasher.
7. Inspect the drain hose for blockages or kinks.
8. Remove any clogs with a length of wire or plumber’s snake and running water.
9. Straighten out any kinks.

4. The check valve is faulty

Thermador dishwashers have a check valve that prevents drained wastewater from re-entering the dishwasher. This one-way valve ensures clean dishes aren’t contaminated by dirty water flowing back into the tub.

Follow these steps to check if the check valve is faulty:

1. Turn off your Thermador dishwasher’s power and water supply.
2. Remove the lower access panel at the bottom front of the dishwasher. It will be secured with screws.
3. Remove the locking collar securing the drain hose to the sump by lifting it up.
4. Pull the drain hose out of the sump.
5. The check valve is located inside the opening where the drain hose is connected.
6. Use a flat-head screwdriver to turn the check valve counterclockwise so it releases. Then pull it out.
7. If the check valve is dirty or clogged, clean it and reinstall it to see if that fixes the drainage issue.
8. If the check valve is damaged, replace it with a new one.

5. The drain pump is faulty

Your Thermador dishwasher’s drain pump removes dirty water from the tub during each wash cycle by pumping it out via the drain hose into your home’s drainage system.

If the drain pump has failed, it will need to be replaced in order to get your dishwasher draining again. Follow these steps to check and replace it:

1. Turn off your dishwasher’s power and water supply.
2. Remove the lower access panel by unthreading the screws securing it.
3. Use a screwdriver to press the locking tab on the top of the drain pump and turn the pump clockwise to remove it.
4. Catch any water that spills out with a towel or container.
5. Remove the wire connected to the drain pump.
6. Inspect the old pump for visible signs of damage, such as cracks or worn parts, and test it with a multimeter for continuity.
7. If faulty, purchase a new drain pump and install it by inserting it, turning it counterclockwise, and connecting the wire.

Thermador dishwasher still not draining?

If after following these steps your Thermador dishwasher still isn’t draining, we highly recommend hiring a skilled appliance technician to inspect your appliance. They’ll be able to quickly diagnose the cause of the problem and provide a quote for the cost of the repair. Most drainage issues are fixable on Thermador dishwashers, so it’s worth having an expert take a look.