Pub. Util. Code, § 16574

The board of directors or other officers of the district may not incur any debt or liability, either by issuing bonds or otherwise, in excess of the express provisions of this division. Any debt or liability incurred in excess of those express provisions is absolutely void, excepting that the debt limitations may be exceeded where the district finances waterworks or sewage disposal facilities by means of a revenue bond issue, or by means of a general obligation bond issue, or by means provided by Section 16580 and makes provision to pledge, as additional security for the general obligation or indebtedness, all or any part of revenues received from the facilities over a period not to exceed 40 years, in which event the limitation of indebtedness set forth in Section 16573 of this code may not be applicable to the bonds or indebtedness so secured or so additionally secured by the revenue.