Cal. Water Code - WAT § 51660. Section 51660.
Any parcel purchased by a county treasurer at delinquency sale, as trustee for the district, may, after approval of the board, be sold and conveyed by him at any time after the expiration of the redemption period at public or private sale, with or without notice, to any person paying him the aggregate amount for which the parcel was purchased, with interest thereon at the rate of 7 percent per year, compounded yearly from the date of each delinquency sale, and:
(a)
When the parcel was purchased at a sale for the delinquency of an unbonded assessment, any unpaid call that has been made upon any prior or subsequent assessment, with accrued interest and penalties thereon.
(b)
When the parcel was purchased at a sale for the delinquency of a bonded assessment, the amount of all subsequent assessments then delinquent, with accrued interest and penalties thereon.