The difference in washing performance between the bottom rack and the top rack of a dishwasher is primarily due to the way water is distributed and the position of the heating element.
Water distribution: In most dishwashers, the water spray comes from the bottom and the sides. When dishes are placed on the top rack, they are closer to the water spray, resulting in better cleaning efficiency. On the other hand, the water spray from the bottom may not reach the items on the bottom rack as effectively, leading to less thorough cleaning.
Proximity to heating element: The heating element in a dishwasher is often located at the bottom. When plastic items or dishes are placed in direct contact with the heating element, they are more likely to be exposed to higher temperatures, which can cause them to melt or warp.
To maximize the cleaning efficiency and prevent plastic items from melting, consider the following tips:
Load plastic items on the top rack: Placing plastic items on the top rack, where they are closer to the water spray and away from the heating element, can reduce the risk of melting.
Proper loading: Ensure that dishes and utensils are loaded in a way that allows water to reach all surfaces. Avoid overloading the dishwasher, as this can obstruct water flow and result in uneven cleaning.
Use the right dishwasher cycle: Some dishwashers have specific cycles designed for delicate items or plastics. Using these cycles can help lower the water temperature and reduce the risk of melting plastic.
Pre-rinse dishes: Scrape off excess food debris before loading dishes into the dishwasher. This can improve cleaning performance and prevent leftover food from adhering to plastic items.
Check dishwasher settings: Some dishwashers have adjustable water pressure and temperature settings. If your dishwasher allows it, consider adjusting these settings to better suit the items being washed.
Remember that not all plastics are dishwasher safe, so always check the manufacturer's instructions or the bottom of the item for dishwasher compatibility before placing it in the machine. Additionally, handwashing particularly delicate or valuable items may be the best option to ensure their longevity and prevent damage.