In paper, the ability to use of the biological early warning systems, in tap water quality biomonitoring was analyzed, based on multiple-criteria decision analysis. Five groups of organisms (invertebrates, fishes, algae, fungi and bacteria) were analyzed for the sensitivity to disturbance, the area of use, the amount of detected components, the rate of reaction and the data interpretation. Both analyzes revealed, that invertebrates are the most sensitive bioindicators (49% AHP, 29% Rembrandt). The other organisms which are useful in BEWS systems are algae and fishes. More problematic may be systems based on fungi and bacteria.Both analysis Rembrandt, as well as analytic hierarchy process(AHP) have indicated the rate of reaction as the most important factor in BEWS. All of BEWS systems are focused on reduce the time required to obtain the information about pollution presence, because the standard monitoring of tap water quality, based on physical and chemical methods, are usually time consuming.