Compliance Standards for Dental Unit Water: Is Your Water Safe?

The Problem

Studies have shown that dental unit waterlines (DUW), which include the small diameter plastic tubing that carries water to air/water syringes, high-speed handpieces, and ultrasonic scalers, can become colonized by a variety of microorganisms at a higher than acceptable level, unless certain protocols are followed. The microorganisms contained in dental unit waterlines are protected by a polysaccharide “slime layer”, which allows them to colonize and replicate inside this biofilm. Biofilms serve as reservoirs that can dramatically increase the number of free-floating organisms in dental unit water.

The Evidence

Although Pseudomonas aeruginosa, Legionella species, and non-tuberculosis Mycobacterium species have been found in dental unit water, most of the organisms recovered in dental unit waterlines have been common heterotrophic water bacteria which have limited pathogenic potential. The problem is that high levels of these bacteria can quickly occur if proper waterline maintenance is not provided. In fact, research has shown levels greater than 200,000CFU/mL in new dental units less than 1 week after installation! Causative factors, in addition to lack of waterline cleaning/disinfection, include poor system design, low flow rates, tortuous curves in the lines, negative flow (“suck-back”) and poor source water quality. These factors, or combinations of them, allow for rapid colonization of bacteria and the development of biofilms.

New Regulations

Water testing is considered extremely important by a number of organizations, prompting both recommendations and regulations. OSAP as well as the EPA recommend quarterly testing of all DUW. The CDC further states that water testing should “follow dental unit manufacturer’s instructions for use.” It should be noted that manufacturers’ state that water should be tested at least quarterly.


Exposing our patients to water of uncertain quality—even below the levels accepted as minimal for drinking water, is inconsistent with accepted infection-control principles, not to mention leaving us in a vulnerable position medically/legally. Current safe drinking water standards, as established by the EPA, the American Public Health Association, and the American Water Works Association, call for bacteria levels < 500 CFU/mL. For this reason, the levels in dental unit water should be as low as possible, but at a minimum, ≤ 500 CFU/ml. Each dental unit should be tested at least quarterly to make sure water quality is at the proper level. Easy-to-use in-office test kits are available.

The Benefits

By following recommendations for dental unit waterline maintenance, we not only provide better treatment for these patients, but liability protection for our business, which is expected to uphold minimum standards for infection control.

Karson L. Carpenter D.D.S serves as president of Compliance Training Partners, a company dedicated to compliance issues in the dental office.

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