Since there is a problem in the sanitary protection of water reservoirs, nitrification inhibitors (NI), such as CMP, HMMP, ATG, were tested for their effects on the organoleptic properties and sanitary regimen of model water basins. The threshold concentrations of the inhibitors were found to be 0.49, 230, and 229 mg/l, respectively. The agents were classified as highly stable. They failed to affect on self-clearance. In chronic intoxication, the inactive doses were 0.128 mg/kg for CMP, 0.165 mg/kg for HMMP, and 1.36 mg/kg for ATG (1/1000 of LD50). The maximum allowable water concentrations were 0.01, 0.01, and 0.1 mg/l, respectively (in the context of complex sanitary standardization). The limiting hazard index was sanitarily toxicological (Hazard Class 3).