· Michael Blair
A dishwasher that has stopped cleaning well usually has a mechanical or maintenance cause rather than a failed component, and Middle Tennessee hard water contributes to most of them.
The filter
Most modern dishwashers have a removable filter in the base that needs cleaning periodically. Many owners do not know it exists, and a clogged one recirculates dirty water.
It twists out and rinses under a tap in a couple of minutes.
Spray arms
Holes clog with food debris and hard water scale, which is common here. Remove the arms and clear each hole with a pin, then check they spin freely.
Tall items blocking the upper arm from rotating is a loading problem that presents identically.
- Clean the filter in the base regularly
- Clear spray arm holes with a pin
- Check the arms spin freely with the racks loaded
- Run the tap hot before starting a cycle
- Descale periodically in Middle Tennessee water
Water temperature
Detergent needs hot water to work. If the dishwasher is on a long run from the heater, the first fill is whatever was sitting in the pipe.
Running the kitchen tap until it is hot before starting the cycle makes a measurable difference, and it costs nothing.
Hard water
Scale builds inside the machine and on the heating element, reducing performance gradually. A periodic descaling cycle with a dishwasher cleaner addresses it.
Rinse aid also matters more in hard water than the marketing suggests, because it is what prevents spotting as items dry.