Homeowner is concerned about randomly occuring low or cool water from the hot side of the faucet. Gave options for cartridge replacement and water heater replacement. The water heater is approximately 16 years old and is recommended to be replaced regardless of what the cause of the problem may be. Shut off the water to the home and drained the system down. Removed and dispose of the water heater off site. Install the new water heater in a pan with new pipe, fittings, valves, tec. Convert the single wall vent piping to double wall piping. Pressurize the system, remove the air from the lines, and put the water heater into service.