49 CFR § 192.375 - Service lines: Plastic.
(a) Each plastic service line outside a building must be installed below ground level, except that -
(2) It may terminate above ground level and outside the building, if -
(i) The above ground level part of the plastic service line is protected against deterioration and external damage;
(ii) The plastic service line is not used to support external loads; and
(b) Each plastic service line inside a building must be protected against external damage.