Steel conforming to ASTM 183. Grooved fittings shall be malleable iron conforming to ASTM A47, Grade 32510 or ductile iron conforming to ASTM A536, Grade 65-45-12. Mechanical couplings and fittings shall be of the same manufacturer. Before couplings are assembled, pipe ends and outsides of gaskets shall be lightly coated with lubricant approved by the manufacturer to facilitate installation.