Gas and particularly natural gas piping may have traces of sediment or particulates in it, especially if work has been done to the underground piping under the street. To trap any contaminates before they flow into the appliance, blocking the burner and creating problems for the home owner a series of dirt legs are installed. These dirt legs are routinely assembled incorrectly allowing the gas to flow straight through and into the burner as seen in the red circled dirt leg. The only way a dirt leg will work is when it has a right angle in the piping with a dirt leg below the angle as seen in the green circle. the dirt leg should not be shorter than three inches in length.
