Washing dishes by hand should not directly ruin your dishwasher. In fact, washing dishes by hand is a completely separate process from using a dishwasher and shouldn't have any negative impact on the dishwasher's functionality.
Dishwashers are designed to handle dirty dishes and are equipped with powerful jets and cleaning mechanisms to efficiently clean them. Handwashing dishes, on the other hand, involves using soap, water, and your hands or a scrubber to clean the dishes manually. This process doesn't interact with the dishwasher in any way.
However, there are a couple of points to keep in mind:
Pre-rinsing: Some people pre-rinse their dishes before loading them into the dishwasher to remove larger food particles. While this is not strictly necessary with modern dishwashers, it can help improve the dishwasher's efficiency. If you're handwashing the dishes and then putting them in the dishwasher without pre-rinsing, the dishwasher might have to work a bit harder to remove stubborn, dried-on food particles. But this shouldn't cause any long-term damage to the dishwasher.
Avoid dishwasher-unfriendly items: When washing dishes by hand, you might have a better awareness of which items can't go into the dishwasher, such as wooden utensils, delicate glassware, or certain plastic containers. Handwashing allows you to avoid the risk of accidentally damaging these items in the dishwasher.
Mineral deposits: If your water supply has high mineral content, it could leave deposits on both your handwashed dishes and the dishwasher's interior. Regularly running a dishwasher cleaner can help prevent mineral buildup and keep your dishwasher functioning optimally.
In summary, washing dishes by hand should not ruin your dishwasher. In fact, it can be an efficient way to save energy and water if you only have a few dishes to clean. Just be mindful of pre-rinsing dishes if you plan to put them in the dishwasher later, and be cautious about placing dishwasher-unfriendly items inside the machine.