Plumb Supply Co., based in Des Moines, announced Friday that it has purchased Riback Supply Co., which is based in Columbia, Mo. Both companies specialize in materials for plumbing, heating, air conditioning, ventilation, and pipe, valves and fittings. The deal is expected to close in the second quarter of 2015; financial terms were not disclosed by the two family-owned companies. Founded in 1946, Plumb Supply operates in 18 locations in Iowa. Riback Supply has 17 Missouri locations and one in Kansas and will continue to operate under that name in its markets. “The combined strength of our two companies will help assure our future, provide solid careers for all our employees and enhance the service and products we offer our customers,” said Scott Anshutz, president of Plumb Supply.