The WSSC, a public corporation, at its option, and if in its opinion the application of this section does not seriously affect the sale of its securities, may waive the required guarantee of Montgomery and Prince George's counties of its bonds and certain other securities, as now required by law; but this section shall not be taken to mean that the waiver of the guarantee on any one issue of its bonds or securities shall be construed to be a waiver of the guarantee of all future issues of its bonds or securities. It is the purpose of this section to permit the WSSC to waive the present requirement of law as to the guarantee of its bonds and securities by Montgomery and Prince George's counties where money market conditions seem to justify the sale of the securities of the sanitary district without such guarantee but to require such guarantee where monetary conditions seem to require the guarantee to secure a favorable sale of its securities.