by Steven Maviglio Flexible, stainless-steel pipe has become the first choice for relining chimneys with offsets. The one shown (Z-Flex, Manchester, N.H.) comes in 25-foot sections that twist-lock at the joints. CHIMNEY RELINING OPTIONS New flue systems offer safety, durability, stove and better performance. Most homeowners find out the hard way about chimney relining: They have a chimney fire. Or their stove or fireplace wafts smoke into their living room on a regular basis. Put simply, unlined chimneys are problem chimneys. First, they are safety risks: 2,100ø Fahrenheit heat, sparks, and even flames can escape from a weak chimney through crumbling mortar and torch the surroundings fairly quickly. In addition, an unlined chimney can't be cleaned properly. Tar-like creosote can find its way into the smallest crevice in an unlined chimney,