Thermador Dishwasher: not draining

Professional Repair Guide

What is this symptom?

Experiencing issues with your Thermador dishwasher not draining? Pooled water at the bottom and early cycle stops are common symptoms. This can lead to dirty dishes and potential error codes like E24/E25. The problem may stem from blockages in the filter, drain pump, or hose, impacting wastewater evacuation. Learn how to identify and resolve these issues effectively.

Urgency: Medium

Important Tips for Thermador Models

Thermadorâ€™s official guidance for draining issues emphasizes cleaning the filter and unblocking the drain pump; for E24, Thermador specifically notes checking the drain hose for kinks/damage and ensuring the pump cover under the filter is not loose.
Thermador installation guidance highlights that the drain hose must have a properly positioned high loop and the total drain hose length (including to air gap) must not exceed certain limits to ensure proper pumping.

Possible Causes

Blocked filter and/or debris in sump area restricting water flow to the drain pump

How to Identify: Standing water with visible food debris; filter appears dirty/slimy; drain pump sounds strained or quiet; problem improves temporarily after cleaning filter.

Part: Filter assembly / sump

Drain pump obstruction (glass, bones, labels) or loose pump cover preventing proper pumping

How to Identify: Humming/whirring during drain but no water evacuation; impeller does not spin freely; debris found under filter near pump cover; some models show E24 and Thermador notes pump cover may be loose.

Part: Drain pump / pump cover

Kinked, clogged, or improperly installed drain hose (including missing/incorrect high loop) causing backflow or slow drain

How to Identify: Water drains slowly or backs up; hose is kinked behind unit; recent installation or moved dishwasher; hose not routed with a proper high loop; improves after correcting routing/clearing hose.

Part: Drain hose / high loop installation

Clogged sink/disposal connection or clogged air gap (where installed) blocking dishwasher drain path

How to Identify: Sink/disposal drains slowly; dishwasher drains poorly only when connected to disposal; air gap overflows or leaks; clearing disposal inlet/air gap restores draining.

Part: Air gap / garbage disposal inlet / sink drain connection

Stuck or failed check valve/check ball allowing backflow or preventing discharge

How to Identify: Water partially drains but returns into tub; repeated small pool of dirty water after cycle; drain pump runs but discharge is inconsistent; inspection reveals stuck check valve/ball.

Part: Check valve / check ball (anti-backflow valve)

Drain pump motor failure (pump runs weakly or not at all)

How to Identify: No drain sound at all or only a low hum; breaker not tripped; filter/drain path cleared but still no draining; pump fails continuity tests (technician-level.

Part: Drain pump motor

DIY Solutions

Clean the filter assembly and sump area (most common fix)

Easy 10-20 minutes

Tools Needed: Gloves, Soft brush/toothbrush, Towel, Warm water

Turn off power to the dishwasher at the breaker for safety.
Remove the bottom rack.
Remove the filter assembly at the bottom of the tub.
Rinse filter components under lukewarm water and gently scrub off grease/food particles.
Wipe out any debris in the sump area beneath the filter.
Reinstall the filter securely and run a short cycle to test draining.

⚠️ Safety First: Cut hazard: broken glass can lodge in the filter/sump areaâ€”wear gloves.

Clear debris from the drain pump and verify the pump cover is seated (E24-related fix)

Moderate 20-40 minutes

Tools Needed: Gloves, Flashlight, Spoon or needle-nose pliers (for debris removal)

Turn off power at the breaker.
Remove the bottom rack and filter assembly.
Locate the drain pump cover beneath the filter area and ensure it is not loose.
Inspect for debris (labels, seeds, glass) around the pump inlet/impeller area and remove carefully.
Reinstall the pump cover and filter securely.
Run a drain/cancel function or short rinse cycle to confirm proper draining.

⚠️ Safety First: Use gloves; sharp debris is common near the drain pump.

Inspect and correct drain hose routing (kinks, clogs, and high loop)

Moderate 30-60 minutes

Tools Needed: Screwdriver, Bucket/towels, Flashlight

Turn off power at the breaker.
Pull the dishwasher out carefully (if needed) to access the drain hose behind the unit.
Check for kinks, crushing, or sharp bends in the hose and straighten as needed.
Confirm the hose has a proper high loop.
If you suspect a clog, disconnect the hose from the sink/disposal end and flush it (have a bucket ready).
Reconnect and test a drain cycle.

⚠️ Safety First: Water spill risk: keep towels/bucket ready.

Clean the air gap and/or disposal dishwasher inlet (if applicable)

Easy 10-25 minutes

Tools Needed: Gloves, Small brush, Screwdriver (sometimes), Towel

If your sink has an air gap (small cylinder near faucet), remove the cap and clean debris inside with a brush.
Disconnect the hose from the air gap or disposal inlet and inspect for blockage.
If connected to a garbage disposal, ensure the dishwasher inlet is not clogged (and if newly installed disposal, confirm the knockout plug was removed).
Reassemble and run a drain test.

⚠️ Safety First: If working near disposal blades, ensure disposal power is off.

Professional Repairs

Replace drain pump (failed motor or damaged impeller)

Estimated Cost: $200 - $600

Replace or service check valve / non-return valve to prevent backflow

Estimated Cost: $180 - $450

Resolve internal blockage in sump/drain path requiring teardown

Estimated Cost: $250 - $700

When to Call a Professional

Water remains after cleaning filter and checking/clearing drain pump area and the dishwasher still will not drain.

Drain pump makes a loud grinding sound, only hums, or does not run at all during a drain cycle (possible pump failure).

You see repeated Thermador drain-related error codes (such as E24/E25 on some models) that return immediately after clearing the pump/filter area.

There is leaking underneath the dishwasher after hose manipulation or the drain system has been modified and you cannot confirm proper installation.

You suspect an internal sump blockage or need electrical continuity testing of the pump.

Preventive Maintenance

Rinse and scrub the dishwasher filter and filter components under lukewarm water to remove grease and debris.: Drain pump blockage and slow/no-drain conditions
Frequency: monthly (or more often with heavy use)
Scrape excess food from dishes before loading (especially seeds, bones, labels).: Sump and drain pump clogs
Frequency: every load
Inspect the air gap (if installed) and clean it if you notice slow draining or backup.: Drain backups caused by air gap obstruction
Frequency: every 3-6 months
Verify drain hose routing remains in a proper high loop and is not kinked behind the dishwasher.: Backflow and drainage failure from improper hose routing
Frequency: after installation, moving the dishwasher, or annually

Frequently Asked Questions

Why is my Thermador Dishwasher not draining?

Common causes include blocked filters, drain pump obstructions, and issues with the drain hose.

How do I fix Thermador Dishwasher not draining myself?

Clean the filter, check the drain pump, and inspect the drain hose for kinks or clogs.

How much does it cost to fix not draining?

Professional repairs can range from $180 to $700 depending on the issue.

When should I call a technician for not draining?

Call a technician if DIY fixes fail or if you suspect a major issue like a failed pump.

References & Sources

Community Analytical Insights

Analysis based on real user discussions from appliance repair communities

Can I Fix This Myself?

50%

DIY Success Rate Difficulty: Either

Common Issues Reported by Users

Pump issues (3 mentions)
Float switch malfunction (1 mentions)
Control board failure (1 mentions)

User Suggested Solutions

Check for water in the base pan and inspect the solenoid for water inlet issues

Success rate: 20.0%
Inspect and potentially replace the pump

Success rate: 20.0%

Analysis based on 5 community discussions
View Sources

Data compiled from real discussions on r/appliancerepair and r/Appliances:

Community Discussions

Makes a draining sound but won’t do anything else

Check for water in the base pan and the solenoid for water inlet issues.

DIY View on Reddit →

not draining

The pump was intermittently functioning; potential issues with the float switch or control board.