Abstract: A water heater comprising a closed tank having a water inlet for connection with a water supply, and a hot water outlet connected to the tank interior; a flue pipe extending vertically through the tank and having an upper portion for connection with a vent pipe; a cylinder having a lower end and upper open end with means for opening disposed within the flue pipe, and spaced from inner walls of the flue pipe, and extending substantially the length of the flue pipe; a burner disposed in a lower region of the cylinder and above the lower end thereof, such that combustion products from the burner rise through the cylinder; and a water conducing coil disposed within the cylinder connected with the interior of the tank.

Abstract: A water heater for heating water containing particulates comprises a recirculating path responsive to water and particulates in the heater. The recirculating path removes particulates from the water flowing therein and returns water with particulates removed from it to the heater. The path includes a particulate filter for removing particulates from the water flowing in the path and a pump for pumping water in the path back into the heater. The path is responsive to a liquid cleaning agent applied to the heater with the water returned to the heater.

Abstract: An automatic self-cleaning electric or gas water heater has a sloped conical bottom wall and a manifold such that water flowing through the manifold gently washes sediment to the bottom wall. The sediment slides along the bottom wall to a bottom drain. The sediment and water in the tank bottom periodically flow through the drain by operation of a controller which activates a solenoid valve.