Abstract: A method of cleaning and maintaining potable water distribution systems which have reduced flow due to an increase of scale, tuberculation, sediment, and the like on the inside surface of the pipe is disclosed. An aqueous acidic cleaning solution is heated and circulated through the pipe to be treated for a sufficient time to dissolve and loosen the scale and sediment, and the spent solution containing dissolved or suspended scale and sediment is flushed from the pipe to provide a cleaned pipe with improved water flow. It is also desirable to flush the water distribution pipe system with high pressure water after the treatment to remove loosened scale and sediment that was not removed during the circulation and flushing of the treating solution.

Abstract: A method of cleaning and maintaining a hot water heater tank contaminated with water scale and sediment by introducing an aqueous acidic treatment solution, retaining the acidic solution for a sufficient time to dissolve or suspend said scale and sediment, and then draining the spent solution containing the dissolved or suspended scale and sediment to provide a clean hot water heater tank.

Abstract: A system is described for diagnosing the operation of an exhaust gas recirculation system of an internal combustion engine having a speed density fuel delivery system and having a closed loop fuel adjustment. The EGR system operation is determined by disabling the EGR system and observing the magnitude of change of the integral adjustment of the closed loop system.