N.Y. Comp. Codes R. & Regs. tit. 16, § 563.14 – Supply, transmission and distribution mains.

(a) All mains, pipes, aqueducts, canals or other facilities for carrying water shall be classified according to their primary functional use as follows:
Supply mains
Transmission and distribution mains
Fire mains
(b) Supply main means any main, pipe, aqueduct or canal the primary purpose of which is to convey water from one unit to another unit in the source of supply, water treatment or pumping plant and generally providing no service connections with customers.
(c) Transmission and distribution main means any main the primary purpose of which is to convey water, requiring no further processing except incidental chlorination or pressure boosting, from a unit in the source of supply, water treatment or pumping plant to customers.
(d) Fire main means any main forming part of an integrated system used exclusively for fire protection purposes.