If there is water at the bottom of the dishwasher after the wash cycle has completed, the drainage system has failed, which often indicates a blocked drain hose or a faulty drain pump. Water remaining in the tray not only makes it difficult to remove clean dishes, but can also cause an unpleasant odor or activation of the leakage protection system AquaStop. Ignoring this symptom can lead to more serious consequences, including failure of the heating element or control module due to a short circuit.
The first thing to do when you find liquid in the chamber is to visually inspect the space under the sink and check whether the drain hose leading from the machine to the sewer is kinked. Often the cause is a simple blockage in the siphon or a filter mesh clogged with food debris, bones or fat that has frozen in the pipes. Before calling a specialist, you should exclude these simple options, since they do not require special tools and can easily be fixed independently at home.
Mechanical obstructions and blockages in the filtration systemThe most common reason why The dishwasher did not drain the water, is a physical barrier to the movement of fluid. During operation, large food debris, bones, toothpicks and even small objects such as coins get into the machine, which can get stuck in the corrugation or impeller of the pump. The filtration system, consisting of coarse and fine filters, is designed to catch debris, but if not cleaned regularly, it becomes a dense plug that blocks the outflow.
To fix the problem, you need to dismantle the lower basket and unscrew the filter element located at the bottom of the chamber. Rinse the mesh thoroughly under hot water and detergent, removing any grease that may have stuck small particles of dirt together. It is also worth checking the hole where the filter usually sits, carefully removing visible debris from there, but this must be done carefully so as not to push the foreign body deeper into the system.
- 🧼 Food residues and fat forming a dense plug in the filter.
- 🦴 Fruit pits, seeds or small bones stuck in the pipe.
- 🥄 Random small objects: coins, buttons, toothpicks.
⚠️ Attention: Never use sharp metal objects (knives, knitting needles) to clean the drain holes, as this can damage the plastic housing or push debris further into the drain pump, complicating repairs.
Problems with the drain hose and sewer connectionEven if the internal filters are clean, water may not drain due to problems with communications outside the machine body. The drain hose is a corrugated tube that is prone to kinks, especially if the dishwasher is built-in and is located in a narrow niche. When installing equipment, a sufficient length margin is often forgotten, and when retracting the housing, the hose is compressed by the walls of furniture or sharp corners, blocking the flow of liquid.
Another common scenario is a clog at the connection to the sewer pipe. If the drain is embedded in a sink siphon or a common riser, fatty deposits accumulate there over time, narrowing the lumen. Water from the dishwasher simply cannot overcome the resistance and remains inside. You can check this by disconnecting the hose from the sewer and lowering it into a bucket: if the pump hums and the water leaves, then the problem is definitely in the sewer pipe.
Incorrect connection may also be the cause. If the hose is not raised to the required height (usually 40-60 cm) before entering the sewer, a siphon effect may occur when water from the sewer flows back into the machine, or the pump cannot cope with pumping due to the lack of the required height difference. Make sure that the hose loop is secured to the rear wall of the machine or cabinet wall with special fasteners.
Malfunctions of the drainage pump (pump)If mechanical obstacles are excluded and the hose is free, and dishwasher still does not drain the water, there is a high probability of failure of the drainage pump. This device is responsible for forced pumping of liquid from the chamber. A sign of breakdown is often a characteristic hum, buzzing or clicking sound coming from the bottom of the housing during draining, while the water remains in place.
The pump may not work for several reasons: the motor winding has burned out, the impeller has jammed due to small debris (glass fragments, bones) or the starting capacitor has failed. In some models, the impeller can be freed from a foreign object by reaching it through the bottom, but more often a complete replacement of the assembly is required. Diagnosing the performance of the motor requires a multimeter to check the continuity of the circuit.
How to test a pump with a multimeter
To check, disconnect the machine from the network, remove the bottom panel, find the pump contacts and ring them. The resistance should be within normal limits (usually 100-200 Ohms). If the device shows an open or short circuit, the pump is faulty.
It is important to distinguish between symptoms: if the pump is silent and does not make any sounds, the problem may not be in the pump itself, but in the lack of voltage supply from the control module. If the pump hums but does not pump, it means either it is jammed or the impeller itself is broken. In both cases, the lower part of the unit will need to be disassembled and the part will probably need to be replaced.
Clogged and broken drain valveThe design of many modern dishwashers, especially premium brands like Bosch or Siemens, a solenoid drain valve is used. This element controls the opening and closing of the water path. If the valve is clogged or its mechanism is stuck in the closed position, the water will physically not be able to leave the machine, even if the pump is working.
The valve becomes clogged with the same contaminants as the filter: grease, scale, small particles. Unlike the main filter, the valve is located deeper in the hydraulic system and is more difficult to reach. Partial disassembly of the housing is often required. If the valve is solenoid, it may burn out, and then it simply will not receive a signal to open.
Helpful advice: Before replacing the valve, try blowing it out or rinsing it under strong water pressure after removing it. Sometimes this helps restore its functionality without purchasing a new part.
Checking the valve includes a visual inspection for scale and coil continuity. If the coil does not ring, it means it is broken and the valve must be replaced. It is also worth checking the wires suitable for it for oxidation or damage by rodents, which happens if the machine is standing on the floor or in the basement area.
Electronics and control module errorsA modern dishwasher is a complex computerized appliance. If all mechanical parts are in good condition, water drains freely during manual check, but the drain cycle does not start, the reason may lie in the “brains” of the device. The control module could freeze, experience a program failure, or fail due to a power surge.
In this case, an error code will often (but not always) light up on the display, indicating a problem with the drain. For example, at Bosch this could be a mistake E24 or E25, y Electrolux — i03 or i04. Deciphering the code helps narrow down your search. Sometimes a simple reboot helps: disconnecting the machine from the network for 15-20 minutes allows you to clear errors and restore the system.
If the reboot does not help, the triac on the board, which is responsible for supplying voltage to the pump, may have burned out, or the pressure switch (water level sensor) has failed. The pressure switch can “lie” to the module, reporting that there is no water in the machine, and then the drain command will simply not be generated. Diagnostics of electronics requires special knowledge and equipment, so in such cases it is often more advisable to contact a professional technician.
Seasonal problems and freezing of communicationsFor owners of dishwashers in private homes or country houses, a seasonal problem is relevant. If the equipment is installed in an unheated room, in winter the water in the drain hose or siphon may freeze, creating an ice plug. In this case, no manipulations with the filters will help until heat access to the communications is ensured.
It is also worth mentioning the problems with the central sewerage system. If the common riser in an apartment building is clogged, water from the upper floors can back up from below, preventing your car from draining the water. This is easy to check: if water does not come out of the kitchen sink, the problem is definitely not in the dishwasher.
☑️ Checklist for primary diagnostics
Comparison table of symptoms and causesFor ease of diagnosis, a table is provided below to help compare the observed symptoms with the most likely causes of the malfunction. This will help you quickly determine where to look for the problem.
| Symptom | Probable Cause | Difficulty in eliminating | Required actions |
|---|---|---|---|
| The water is standing still, the pump is silent | Electronics failure, open circuit, pressure switch | High | Reboot, continuity test, sensor replacement |
| The pump is humming, but the water does not flow out | Blockage in the pump, hose or siphon | Average | Cleaning the system, removing debris |
| The water goes away slowly | Partial blockage, pump wear | Low | Washing filters and hoses |
| Error code appears | Malfunction of a specific node | Depends on the code | Deciphering the code, diagnostics of the unit |
⚠️ Attention: Unless you have electrical skills and know how to safely disassemble the equipment, do not attempt to repair the control module or pump yourself. This may be life-threatening and will void your warranty.
Prevention of blockages and proper careTo prevent the question “why didn’t the dishwasher drain the water” from coming up before you regularly, it is important to follow the operating rules. The majority of problems arise from improper preparation of dishes for loading. Food remains, grease and scale are the main enemies of the drainage system.
The main conclusion: 90% of drainage problems can be solved by regular cleaning of filters and proper preparation of dishes before loading.
The main conclusion: 90% of drainage problems can be solved by regular cleaning of filters and proper preparation of dishes before loading.
It is recommended to carry out preventive cleaning once a month using special products for cleaning dishwashers from grease and scale. It is also worth periodically checking the condition of the drain hose and changing it if necessary, since over time the corrugation inside becomes overgrown with deposits.
- 🍽️ Always remove large food residues from plates before loading.
- 🧽 Wash filters regularly (once a week) under running water.
- 🧪 Use salt and rinse aid to soften the water and prevent scale.
What to do if there is soap scum left in the car?
If you see a lot of foam instead of clean water, it means that the wrong detergent was used (for example, hand washing gel) or too much of it. Foam is blocking the pump. It is necessary to run the rinse mode several times, adding a spoonful of vegetable oil, which extinguishes the foam.
Is it possible to operate the machine if it has not completely drained the water?
Strongly not recommended. Remaining water leads to the growth of bacteria, mold and an unpleasant odor. In addition, the next time you turn on the machine, it may not start the wash cycle due to an error in the water level sensor.
How often should the drain hose be replaced?
The service life of a drain hose is on average 5-7 years. However, if you notice cracks, hardening of the rubber, or an unpleasant odor that does not go away after cleaning, it is better to replace the hose sooner.