Went out on an isolation valve replacement today that should have been pretty straight forward.... NOT!!! First, ran into gas line marking tape. Then found out that the 2-1/2" main line had been reduced to 2" the first 10' where it takes off from a 3" main line. Oh well... jettison the Dresser couplings, use reducer bushings and just glue the damn thing on as space was quite limited.