Legionella pneumophila is a Gram-negative bacteria whose natural habitat is water, including rivers, lakes and streams. L. pneumophila causes Pontiac fever and Legionnaires' disease with some of the water sources of infection being water distribution systems, cooling towers and humidifiers. Despite anti-epidemic measures, legionellosis outbursts still occur very frequently and because of that it is necessary to develop new methods to remove Legionella from the water. One of the aproaches is antimicrobial photodynamic therapy, which includes combined activity of photosensitizer, molecular oxygen and visible light of appropriate wavelength to create singlet oxygen and oxygen reactive species leading to cell death. In this study we compared the activity of the newly synthesized amphipathic porphyrin with two hydrophilic porphyrins for possible photodynamic inactivation of bacteria in the tap water. The results were derived from the determination of minimum inhibitory and minimum bactericidal concentration in broth and minimum effective concentration in tap water by the microdilution method. A red light with the total dose of light 7,2 J cm-2 or 24 J cm-2 was used and violet light with total dose of light 12 J cm-2. The most efficient compound was amphiphilic porphyrin while the activities of the hydrophilic porphyrins differ minimaly but in favor of the tetracationic porphyrin. Longer illumination with lower dosage of red light was shown to be more effective than shorter illumination with red light with higher fluence rate and higher total dose of light probably due to the longer exposure of bacteria to the light. In the sterile water, compounds showed antimicrobial activity without illumination, but the toxicity increases after light activation.