The answer to 'why is my water heater clogged' is that a buildup of sediment, mineral deposits, or debris can clog the water heater over time. This can restrict water flow and reduce the efficiency of the water heater. Common symptoms include reduced hot water output, longer heating times, and strange noises coming from the tank.
To resolve a clogged water heater, you can try flushing the tank to remove the sediment buildup. This involves connecting a hose to the drain valve at the bottom of the tank and draining several gallons of water. If that doesn't fix the issue, you may need to have a professional plumber inspect and clean the tank, or potentially replace the water heater if it's older and the problem persists.