1. Bonds of any such sewer district, payable from taxes, may be issued for the purpose of improving and extending the sewerage system of the district upon the approval of a proposition to issue such bonds by the constitutionally required percentage of the voters voting on the question.
2. The question shall be submitted in substantially the following form:
3. Before any sewer district shall incur any indebtedness evidenced by bonds payable from taxes as hereby authorized, such sewer district shall provide for the collection of an annual tax on all taxable tangible property therein sufficient to pay the interest and principal of the indebtedness as they fall due and to retire the same within twenty years from the date contracted.