(a) A water district, as defined in subdivision (b), in existence prior to May 18, 1994, that provides primarily agricultural services through a piped water system with only incidental residential or similar uses shall not be considered to be a public water system if the department determines that either of the following applies:
(1) The system is providing alternative water for residential or similar uses for drinking water and cooking to achieve the equivalent level of public health protection provided by the applicable primary drinking water regulations.
(2) The water provided for residential or similar uses for drinking, cooking, and bathing is centrally treated or treated at the point of entry by the provider, a passthrough entity, or the user to achieve the equivalent level of protection provided by the applicable primary drinking water regulations.
(b) For purposes of this section, “water district” means any district or other political subdivision, other than a city or county, a primary function of which is irrigation, reclamation, or drainage of land.