A polyolefin composition for pipes comprising (percent by weight): A) from 1% to 9.5%; of a copolymer of propylene and hexene-1 wherein said copolymer comprises from 0.1 to 5% of recurring units derived from hexene-1; B) from 80.5% to 99% of a heterophasic polypropylene composition comprising: B1) from 50% to 85% of a propylene homopolymer, said propylene polymer being insoluble in xylene at ambient temperature in an amount over 85% having a polydispersity Index ranging from 3 to 10; and a Melt Index from 0.5 to 10 dg/min; B2) from 5% to 50% of a copolymer of ethylene and propylene having an ethylene derived units content ranging from 30% to 70%; said polymeric composition having a Melt Index from 0.05 to 10 dg/min.