When any routine or repeat sample is total coliform-positive, the supplier of water shall analyze that total coliform culture medium for fecal coliform or E. coli. The Approving Authority may allow a public water system to forego the fecal coliform or E. coli analysis if the supplier of water assumes that the total coliform-positive is fecal coliform-positive or E. coli-positive and reports this to the Approving Authority in accordance with Regulation .19 of this chapter. The fecal coliform and E. coli analysis shall be conducted in accordance with methods specified in 40 CFR §141.21(f), which is incorporated by reference.