Arrived at customer’s house to a leaking 40 gallon natural gas water heater. The nipples on the inlet and outlet connected to the mixing valve had some corrosion but no water was visibly leaking from the top of the tank. Removed the burner compartment door and did not see any signs of moisture inside. A significant amount of water was on the carpet in front of the tank. Vacuumed up Al the water and ran hot fixtures throughout the house and saw some signs of water moving from the bottom of the tank towards the carpet. Shut off water to the tank. Shut off gas and turned off the water heater. Drained the tank. Cleaned up work space. Checked for leaks again with none found. Please call customer in the morning to inform them of what time we will be back out here to change out their water heater.