The answer to 'sink constantly running' is that the most common causes are a faulty or stuck flushing mechanism in the sink drain, a leaky faucet, or a problem with the sink stopper. This can lead to water constantly draining from the sink, even when not in use.
Some common symptoms include the sink making a constant gurgling or running sound, water continuously dripping or flowing down the drain, and higher-than-normal water bills. Solutions can range from simple DIY fixes like adjusting or replacing the sink stopper, to more complex issues that require a professional plumber to repair or replace faulty faucet components or piping.