The answer to 'how to fix water heater installation' is to first turn off the power or fuel supply to the water heater, then drain the tank, and finally replace any faulty components. This may involve adjusting the thermostat, replacing the heating element, or addressing issues with the tank or connections.
It's important to follow all safety precautions, including wearing protective gear and shutting off the power or fuel source before working on the water heater. Attempting to fix a water heater without the proper knowledge and tools can be dangerous, so it's often best to call a professional plumber, especially for complex repairs or installations.