Infection control was an effort to prevent the spread of microorganisms, both from patient to another, the patient to the operator, the operator to patients, operators and the environment to the environment to the patient. Effective infection control was one of the important indicators show the achievement of the implementation of oral health care was good. This study aimed to quantified the number of colonies and identified the bacteria in the water that pass through the Dental Unit Waterline (DUWL) in the dental unit Dental Hospital Faculty of Dentistry, Andalas University. The research did with patch the water from a high-speed handpiece, water syringe and ultrasonic scaler. Based on the study formula Federer (2007) gained as much as 9 samples in one group of tools. Thus, the samples totaling 27. Samples were obtained using simple random method. Colony counting and identificated of bacteria carried in Health Laboratory the West Sumatra Regional using blood Agra media. The results showed that there were 22 samples of water contaminated by bacteria, 4 of which were not in accordance with ADA standards. Gram-positive cocci bacteria contamination as much as 8 samples and Gram-negative bacilli as many as 16 samples. Klebsiella pneumoniae bacteria found in two samples of water through the water syringe. Thus, the dental unit waterline on the dental unit has potential as a source of microorganisms, particularly bacteria.
 Keywords:Control infection, bacterial contamination, dental unit waterline, high-speed handpiece, water syringe and ultrasonic scaler