Pub. Util. Code, § 13372

The district may issue refunding bonds, notes, or other evidences of indebtedness for the purpose of paying and redeeming at or before maturity any bonds, notes, or other evidences of indebtedness issued under this chapter, provided that such refunding bonds, notes, or other evidences of indebtedness shall not be in excess of the limitation of indebtedness authorized under this chapter and shall mature in not to exceed seven years from the date of the original indebtedness. Such refunding bonds, notes, or other evidences of indebtedness may in turn be refunded under like terms and conditions, provided that in no event shall such refunding notes mature in excess of seven years from the date of the original indebtedness.