The governing board of the district may at any time reduce or discontinue any revolving cash fund established by its order. Whenever the fund is ordered reduced the person using it shall immediately return to the county treasury the amount necessary to reduce the fund, as ordered by the board. If the fund is discontinued, the person using it shall immediately refund the amount thereof to the county treasurer. In either event a reasonable time shall be allowed the person to reimburse himself by bills presented to the school district for expenditures legally made from the fund.