California Code, Water Code - WAT § 22281.1

A district may establish a charge for the right to connect to new pipelines or extensions of existing pipelines constructed in whole or in part at the expense of the district in such amounts as in the opinion of the board will reimburse the district for the cost of construction advanced by the district.

The connection charge shall be as nearly as possible an amount equal to that proportion of the cost of construction of the new pipeline or extension that the area to be served by the connection bears to the total area to be served by the new pipeline or extension.