The answer to 'drain constantly running' is that a constantly running drain is typically caused by a problem with the drain mechanism or a blockage in the drain line. This can be due to issues like a faulty flapper valve, a stuck drain stopper, or debris buildup in the drain pipe.
Some common symptoms of a constantly running drain include the drain not closing fully, water slowly draining, or the drain making a gurgling or hissing sound. In many cases, this can be a DIY fix, but if the problem persists or you're unable to identify the root cause, it's best to call a professional plumber to diagnose and repair the issue.