Polypropylene pipes (parts by weight): 1) 100 parts of a crystalline random copolymer of propylene with 1-15% by weight of a C.sub.4-C.sub.10 .alpha.-olefin or a crystalline random copolymer of propylene with 1-15% by weight of C.sub.4-C.sub.10 .alpha.-olefin and with 1-7% by weight of ethylene 2) 0 to 70 parts of an elastomeric polyolefin selected from the group consisting of: (a) a copolymer of ethylene with propylene and, optionally a diene, having an ethylene content of from 17 to 45 wt % and an propylene content from 55 to 83 wt %; (b) a copolymer of ethylene with a C.sub.3-C.sub.10 .alpha.-olefin having an ethylene/C.sub.3-C.sub.10 .alpha.-olefin weight ratio of from 29 to 86 wt % (.sup.13C-NMR analysis) and having an Mw/ Mn ratio of less than 3.5; and 3) 0-30 parts of a polymer of ethylene having a melting temperature over 120.degree. C. and intrinsic viscosity of from 2 to 6 dL/g; with the proviso that when the elastomeric polyolefin is present, the polymer of ethylene is at least 12 parts based on 100 parts of the crystalline random propylene copolymer (1) and that at least one of the layer made of the said polymer propylene composition is substantially free from random copolymers of propylene with 15 wt % or less of ethylene as the sole comonomer.