<p>Avian diseases from the bacterial origin in laying and breeding hens are still one of the most frequent causes of economic losses in the poultry sector; they usually cause a decrease in the production of eggs, high mortality and loss of the quality of the eggs, in addition, high costs for diagnosis and treatment. A case report is made of a possible avian colibacillosis in the department of Cundinamarca (Colombia), in a field of 8500 heavy Ross308® breeders of 49 weeks of age, associated with a failure in the water sanitization system. There were analyzed four birds in the facilities of the Avian Pathology Laboratory of the National University of Colombia, reporting by histopathology findings such as ovoperitonitis, salpingitis, hepatitis, and peritonitis compatible with bacterial processes; however, microbiological analyses did not report the presence of microorganisms in the samples of the analyzed organs. At the farm, samples were collected from drinkers, feeders, fecal matter, bedding, nests, and drinking water, isolating Klebsiella spp. and Pseudomonas spp. In storage systems, and water conduction and raised total and fecal coliform counts in water samples by microbiological testing. Failures in water treatment systems were identified as a possible cause of infection. Demonstrating the need to reach a definitive and adequate diagnosis and the establishment of appropriate treatment, by relating the physical evidence on the farm with the use of practices; and to establish the measures to obtain a correct diagnosis.</p>