The answer to 'bathtub constantly running' is that the most common causes are a faulty or worn-out drain stopper, a leaky faucet, or a problem with the overflow drain. This can lead to water constantly running into the tub, even when the faucet is turned off.
Some common symptoms include the tub slowly filling up with water, the sound of running water when the faucet is off, and a higher than normal water bill. Solutions can range from simple DIY fixes like replacing the drain stopper or tightening the faucet, to more complex issues that may require a professional plumber to address problems with the overflow drain or other internal plumbing components.