Mueller made its initial entry in the plastic DWV fittings market through acquisition in the early 90's. Since then, Mueller has acquired additional DWV manufacturing facilities and in 2002 acquired a pressure plastic manufacturing plant. Like other manufacturing operations, these plants receive extensive capital investment to upgrade both the manufacturing process and production capability. Mueller has four manufacturing plants producing plastic fittings; three are dedicated to the manufacture of DWV fittings and one is dedicated to the manufacture of pressure fittings. Mueller has enhanced fittings injection molding with precise process control that ensure consistent product, piece after piece, in every part style.