You can leave the hot water valve off if you always wash in cold. Many washing machines are designed to operate with just the cold water supply when using cold settings. However, it's a good idea to keep both valves on if you plan to occasionally use hot water in the future.
When both valves are open, it helps prevent any potential buildup or blockage in the hot water line, which can occur if it's left unused for long periods. Additionally, some machines may have a feature that uses a mix of hot and cold water for rinsing, so keeping both valves on can ensure optimal performance.
If you're concerned about water usage or wear on the valves, you can safely turn off the hot water valve when not in use. Just remember to turn it back on if you decide to wash with hot water later.
As a next step, if you're unsure about your specific machine's requirements, check the user manual or consider consulting a local appliance repair professional for advice. You can also get 2-3 local quotes on Handyman.com if you need assistance with any plumbing or appliance issues.
— Assisted answer