The situation when a Bosch dishwasher stops draining water often takes you by surprise. Remaining dirty liquid at the bottom of the chamber prevents the cycle from completing, and scary error codes can light up on the display. The owner is faced with the need to urgently solve the problem so that the equipment works normally again.
In most cases, the reason lies in banal blockages or kinks in the drain hose, which can be easily fixed on your own without calling a technician. However, sometimes the problem can be deeper and relate to failure drain pump or clogged sewer system. Understanding the design of the drainage system will help you quickly locate the problem.
In this article we will analyze in detail all possible reasons, from simple to complex, and provide a step-by-step algorithm of actions. You'll learn how to decipher error codes, clean filters, and check electrical components. Competent diagnostics will save your time and budget on repairing expensive equipment.
Primary diagnostics and error codes
Modern models Bosch Serie 4 and Serie 6 equipped with a smart self-diagnosis system. If problems arise with drainage, the machine not only stops, but displays a digital code or a flashing indicator on the screen. This is the first and most important signal to start troubleshooting.
The most common code users encounter is E24. It indicates that the drain pump is not working or is not working efficiently. The machine tries to pump out water, the timer expires, but the liquid level in the pan does not decrease. In older models, the "Finish" indicator or the tap symbol may flash instead of numbers.
Less common error E25, which indicates that the drain pump itself is clogged with foreign objects. In this case, the impeller may hum, but will not rotate, or will do so with difficulty. Ignoring these signals may result in burnout of the pump motor winding.
⚠️ Attention: If you see code E24, do not try to disassemble the machine immediately. In 80% of cases, the problem is solved by simply cleaning the filter system, which will be discussed below.
For accurate diagnosis, it is important to monitor the behavior of the equipment. Is the pump humming? Can you hear the characteristic pumping sound? If the machine is silent, there may be an electronic problem or an open circuit. If it hums, but does not pump water, there is a mechanical blockage or wear of the impeller.
Mechanical interlocks: filters and hoses
The most common reason why Dishwasher doesn't drain water, consists of a physical obstacle in the path of the flow. Food debris, stones, grease and scale build up in the filtration system over time. If the filter is clogged, water simply cannot pass further into the drain pipe.
The second critical element is the drain hose. It may become bent if the machine is moved too close to the wall, or become clogged with debris where it connects to the sewer. The siphon under the sink, where the dishwasher drain is connected, becomes especially clogged.
☑️ Cleaning the drain system
To clean the filter, you need to remove the lower basket and unscrew the cylindrical element clockwise (usually). Then the fine mesh is removed. All elements must be thoroughly rinsed under hot water using a brush and degreaser. The fat film often creates a “plug” effect.
Inspecting the hose requires care. Disconnect it from the sewer and check the passage. If the hose is long and laid under the floor, make sure that it is not crushed by a furniture leg or an adjacent cabinet door. The bend of the corrugation completely blocks the flow of liquid.
Malfunctions of the drain pump (pump)
If the filters are clean and the hose is free, attention turns to drain pump. This is the heart of the drainage system. Bosch dishwashers use two types of pumps: with a magnetic coupling and standard electromechanical ones. Their design may differ, but the principle of operation is the same.
Often small objects get into the pump chamber: toothpicks, glass fragments, fruit pits. They block the rotation of the impeller. In some Bosch models, the pump cover is removable and allows you to remove debris without completely replacing the unit. In other cases, the entire pump may need to be dismantled.
| Symptom | Possible reason | Solution |
|---|---|---|
| The pump is humming, but the water does not flow out | Impeller jammed | Disassembling and cleaning the pump |
| Complete silence when draining | Broken circuit or burnt out motor | Continuity test with a multimeter, replacement |
| A cracking or grinding sound is heard | Shaft bearings destroyed | Replacing the drain pump |
| The water goes away slowly | Impeller wear | Replacing the impeller or pump |
To check the operation of the pump at home, you will need a multimeter. It is necessary to measure the resistance of the motor winding. Normal values vary between 150-200 ohms. If the device shows infinity or zero, the pump is faulty and requires replacement.
How to remove the pump without completely disassembling it?
In some Bosch models (for example, with the Aquastop system), access to the pump is possible from below. Turn the machine over on its side (on a soft surface) and remove the protective bottom. The pump is attached with latches or screws to the sink body. Disconnect the chip and pipes, then remove the assembly.
Problems with sewerage and connection
Sometimes the reason lies not in the car itself, but in the communications at home. If the drain hose is not connected to the sink siphon correctly, a backflow effect or air lock may occur. Water from the sink can flow back into the dishwasher, blocking its operation.
It is important to follow the connection height rule. The drain hose should rise to a height of 50-60 cm from the floor level before entering the sewer. This creates the necessary water seal and prevents dirty water from gravity flowing back into the chamber when the pump is turned off.
A clogged sewer pipe is another common culprit. If the water from the sink does not flow well, then the dishwasher will not be able to push through the flow. In this case, it is necessary to clean the general sewer system using a cable or chemicals.
Use an anti-return valve when connecting a drain. This simple device is inexpensive, but is guaranteed to prevent clean and dirty water from mixing if there is a blockage in the drain.
Electronics and control module
If the mechanical part is working properly, but the water is still standing, the problem may be in the “brains” of the device. The control module issues a command to start the pump. If the relay that controls the pump is stuck or burnt out, the command will not be executed, even if the pump itself is working.
It's also worth checking the wiring. In conditions of constant vibration and humidity, contacts may oxidize or come off. Wires often fray where they exit the machine body or near moving parts. Visual inspection of the harnesses may reveal obvious damage to the insulation.
Power surges in the network could damage the triac on the board. In this case, professional diagnostics with an oscilloscope is required. Self-repair of the control board is only possible if you have in-depth knowledge of electronics and soldering of SMD components.
⚠️ Attention: Before any work on the electrical part, be sure to unplug the dishwasher. Residual voltage on the module capacitors can be dangerous.
Prevention and proper operation
To Bosch dishwasher served for a long time and did not create problems with drainage, it is important to follow the operating rules. The main enemy of the drainage system is fat. It hardens in the hoses and pump into a hard mass that is difficult to remove.
Use special products to clean dishwashers from grease and scale at least once a month. Run the cleaning cycle at maximum temperature with the chamber empty. This will help dissolve deposits in hard-to-reach areas of the drainage system.
Always remove large food particles from plates before loading. Although modern models have shredders, they are not designed for scraps, pits and peels. The entry of such objects into the pump is the most common cause of breakdowns.
Regular cleaning of filters once a week extends the life of the drain pump by 3-5 years and prevents the appearance of an unpleasant odor from the car.
Why doesn't the dishwasher drain the water after first turning it on?
When starting for the first time, there may be air left in the system. Try running the rinse mode. If this does not help, check that all shipping plugs have been removed and that the hose is connected correctly.
Can a cable be used to clean a dishwasher drain hose?
Strongly not recommended. The cable can damage the internal corrugated structure of the hose or pierce it, causing a leak. It is better to remove the hose and rinse it under strong water pressure.
What to do if error E24 appears periodically?
This may indicate incipient wear on the pump or periodic blockages. Check the filter to make sure that no small objects are getting into the pump. If the problem persists, it is better to replace the pump in advance to avoid flooding the kitchen.
How to check if the drain pump is working without disassembly?
Turn on the "Drain" mode (if there is one in the menu) or run a short program. Place your hand on the bottom of the machine (where the pump is). If you feel vibration and buzzing, the pump is working. If there is silence, the problem is in the electrics or the motor itself.