Abstract: A water heater for use in a carpet cleaning system has a pair of inner copper tubes which are press fit into outer copper sleeves. Each tube/sleeve combination defines a heating chamber. A hollow tubular bridge extends perpendicularly between and in fluid communication with the heating chambers. A heating element extends coaxially into each heating chamber. A small annular clearance extends between each heating element and inner tube. High pressure fluid enters one of the heating units through an inlet/outlet port and circulates through the bridge to the other heating unit for additional heating. An electronic thermostat is mounted to the exterior surface of each outer sleeve at a desired location to detect the temperature of the fluid by monitoring the temperature of the exterior surface of the heating unit.