A dishwasher not cleaning dishes properly can have various causes. It’s rarely anything serious. There could be a specific fault such as the motor not running, but this article is more for when the dishwasher appears to run OK and finishes in normal time, but wash results are disappointing.
Choose the correct wash cycle
Obviously. But you have to start here. There aren’t usually many wash cycles to choose from on a dishwasher but you can still get big differences in temperatures, wash intensity and wash results. So make sure you are using the best cycle for the items inside and that you understand all the option buttons and what they do.
Load the dishwasher properly
Poor loading of plates, dishes or trays can allow some items to be shielded from water and detergent. So if it’s just one or two items that aren’t washed properly make sure nothing is being shielded. Load the dishes according to the advice in the instruction manual.
Blocked spray arm
One or more spray arms jammed or otherwise not rotating can cause poor wash results. Check that none of the dishes are physically stopping one of the spray arms from turning. Also check that it rotates freely by hand. Examine all the small holes along each spray arm for blockages (usually bits of food).
Jets of water spraying out of these holes is the only thing that causes them to rotate so blocked spray arms can inhibit movement. Check the instruction manual to see how the spray arms can be removed.
Detergent cover getting jammed
Make sure there isn’t anything in front of the detergent compartment in the door. Most dishwashers have a detergent compartment in the door with a spring-loaded cover. Detergent is placed inside and is dropped into the bottom of the dishwasher when the cover pops open during the wash. If there is a large plate or tray in front of this cover it can prevent the cover from springing open. It could either prevent it from opening altogether or only allow it to partially open. This could prevent the tablet from dissolving properly or cause it to only dissolve slowly over the entire wash cycle instead of on the main wash.
Dishwasher salt and rinse aid
Dishwasher salt and rinse aid are vital for a good wash, especially with hard water. Always make sure you are using proper dishwasher salt and keep topped up with rinse aid to prevent streaks and marks on dishes. If you are using 3 in 1 or other multi tab detergent make sure you have calibrated your dishwasher. This article explains how dishwashers may need calibrating or adjusted to use multi tab detergent have you calibrated your dishwasher for multi-tab detergent?
Streaks or drops of water and lime spots on dishes and glasses
If you are getting streaks or spots on the dishes after washing check out this article – streaks or drops of water and lime spots on dishes and glasses?
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Poor detergent or even wrong type
It should go without saying that the quality of the dishwasher detergent is a major factor. A surprising range of wash results can be attained using different detergents. The consumer group Which? routinely test detergents and some of them are pretty rubbish. Check this article to get more information on how to find the best dishwasher detergents – Which is the best dishwasher detergent?
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