Nitrates (V) in drinking water are harmful to human health and are a probable carcinogen. Nitrates (V) in drinking water are responsible for the formation of methaemoglobin, which causes hypoxia, cyanosis, collapse and even death. Newborn babies and infants up to six months of age are most at risk. For this reason, a European Union directive was introduced in 1991 to protect waters from pollution caused by nitrogenous fertilisers of agricultural origin, restricting their use. The aim of the study was to analyse the content of nitrogen compounds (ammoniacal nitrogen, nitrates (III and V)) in water samples from selected rural waterworks in Tłokinia Wielka. Analyses were performed using spectrophotometric methods. The results showed that excessive levels were present in the tap water from public water supplies, which are regularly monitored by the State Sanitary Inspectorate and water supply companies.