The answer to 'why is my water heater constantly running' is that the water heater is likely not functioning properly and needs to be repaired or replaced. This could be due to a variety of issues, such as a faulty thermostat, a broken heating element, or a problem with the tank itself.
Some common symptoms of a constantly running water heater include the tank never shutting off, the water never getting hot enough, or the unit making strange noises. If your water heater is constantly running, it's important to have it inspected by a professional plumber as soon as possible to diagnose and fix the problem. Leaving it unattended can lead to further damage and higher energy bills.