Sewage disposal facilities shall be connected to the sewage disposal system of the Village. In any district where public sewage service is not available, the width and area of all lots shall be sufficient to permit the use of an on-site sewage disposal system designed in accordance with Wis. Adm. Code H 65. In no case, however, shall the minimum lot size required in the zoning district in which such structure is to be located be reduced below the specified minimum.