As part of my preventive maintenance program around the house, every time I replenish the rinse aid in the dishwasher I also run several sinks full of hot soapy water down the drain. The kitchen sink is on the opposite side of the house from the sewer pipe to the city sewer system. It is good practice. Ever since I have started doing that we have not had any sewer blockages. The hot water goes the length of the house past all the inlets from other sewage sources. Today's effort was satisfactory.