The answer to 'why is my sink constantly running' is that the most common cause is a problem with the sink's internal plumbing components, such as a faulty faucet or a stuck valve. This can lead to water continuously flowing through the sink, even when the faucet is turned off.
Some common symptoms of a constantly running sink include the sound of running water, a wet countertop or floor, and higher-than-normal water bills. The solutions can range from a simple faucet repair to replacing worn-out internal components, such as washers, gaskets, or the entire faucet assembly. While some minor sink repairs can be done DIY, it's often best to call a professional plumber, especially if the issue is more complex or involves the sink's drainage system.