Cal. Water Code § 9565

Any person interested in any tract of land sold at a delinquent sale, made pursuant to the provisions of this chapter, may redeem the tract of land at any time within one year after the date of sale by paying to the county treasurer for the purchaser a sum equal to the purchase price stated in the certificate of sale with interest thereon at the rate of 12 per cent per annum from the date of sale to redemption together with any and all subsequent delinquent installments of the assessment on the land with any and all penalties prescribed for delinquency.