Cal. PUC § 2704

Any owner of a water supply not otherwise dedicated to public use and primarily used for domestic or industrial purposes by him or for the irrigation of his lands, who (a) sells or delivers the surplus of such water for domestic or school district purposes or for the irrigation of adjoining lands, or (b) in an emergency water shortage sells or delivers water from such supply to others for a limited period not to exceed one irrigation season, or (c) sells or delivers a portion of such water supply as a matter of accommodation to neighbors to whom no other supply of water for domestic or irrigation purposes is equally available, is not subject to the jurisdiction, control, and regulation of the commission.