A review is given on the quality of water samples, regularly sent to the LUFA Oldenburg for analysis. Most of the samples derive from reduced groundwater bodies, indicated by a high concentration of iron (Fe, median 3 mg/l) and a low concentration of nitrate (NO3-, median 3 mg/l). Samples from peat land regions often show high concentrations of ammonium (NH4-) and a high oxidability. Samples from near the coast or near a salt mine may contain high salt concentrations. The deviation of the results is usually very high; in individual cases any parameter is able to make the water unusable. Each component may spoil the water for animal consumption if its concentration is too high. A scheme of standard values is given with the 4 graduations safe/enhanced/dangerous/unusable. Kind and age of the animals have to be taken into account, when water is assessed for animal consumption. The intake with the fodder of some substances such as Fe or NO3- is many times higher than the intake with the water.