You have 100ppm of nitrates from the tap? Jeeze. I wouldn't be drinking tap water then. The Safe Water Drinking Act of 1974 had the EPA set an upper limit on nitrates maximum contaminant level goals (MCLG) of 10 mg/L or 10 ppm.
I'd try a different nitrate test kit because 100ppm out of the tap would be a human health issue.
I'd try a different nitrate test kit because 100ppm out of the tap would be a human health issue.