How a Dishwasher Works

In this article we explain how a dishwasher functions at various stages on its cycle. By understanding this it may help you identify what is preventing your dishwasher from working correctly and how to get the best results.

For information on how to tackle and resolve faults and problems on a wide range of appliances see our other articles ».

Advice Articles

Nearly all dishwashers in the UK work in the same manner, by heating and spraying water (containing a low foaming detergent) over the dishes, rinsing and then heating up to help dry the dishes and pans.

Listed below is a typical short wash cycle, some cycles may have a pre-rinse, which is not normally heated.

1) In the first stage of the dishwasher cycle (once the door is closed and the programme is started) the drain pump will turn for around 20 seconds, this is to clear any excess fluids (such as tea or soft drinks) that may have been spilt into the sump whilst loading the dishes.

The usual hum and sound of water draining will be heard, but if this hum is significantly quieter and no water is heard or if the machine will not drain, check the pump for blockages.

2) After the pump has purged the sump of water then the dishwasher will start to fill with its usual hiss and the sound of trickling water. This will continue for typically 20 to 60 seconds.

3) Next, a louder whoosh will be audible as the wash motor starts. If the drain pump starts before the wash motor then this suggests the level sensor has not recognised the presence of water in the machine and the control board has decided to empty the appliance to prevent flooding.

If a hum can be heard, but the water fills and stops without the whoosh sound this may be indicating a wash pump failure.

4) If the machine has drained, filled and started washing then the next stage in the process is for the release of the detergent dispenser several minutes into the wash period. This can be identified by a small thump sound as the flap opens. If this fails to operate correctly it will not stop the cycle.

5) Depending on the cycle selected the dishwasher should be heating the water whilst washing until the programme instructs it to drain. If the wash period is lasting for an excessive time you can check to see if there is a problem by opening the door slowly. This will pause the cycle and you can check if the water shows signs of heating as a heater problem may cause the machine to stick at this stage in the wash cycle.

6) The dishwasher will now try to drain, fill and rinse.

7) If the dishwasher has got to this stage (where it has washed, drained and rinsed) most machines will now start the drying stage of the cycle. This is implemented by the heater warming fresh, clean water close to boiling and, having heated the pots and plates, the machine drains and the latent heat within the pans and plates allows the water droplets to evaporate.

Once the dishwasher bleeps to indicate it has finished the cycle, many manufacturers suggest opening the door to release the steam from the cavity, helping the contents to dry quicker.

It's worth noting that ceramic plates and metal pans are much better retainers of heat than items such as plastic plates or containers, so the drying process will be less effective on plastic items.

If, on inspection, the cause of a fault is not immediately apparent you may require the assistance of a trained professional.

For some common faults on dishwashers view our "common-dishwasher-faults" article.

Dishwasher Accessories

To get the best results from your dishwasher rinse and brush off all food particles before loading the machine.

* All information provided is a guide only. BuySpares accepts no liability for any problems occurred while attempting any advice shown. If in any doubt contact a qualified repair service.

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