Guidelines and Best Practices for Dental Unit Waterline Maintenance

Dental unit waterline (DUWL) maintenance and monitoring remains an area of concern for dental facilities. Agencies such as the CDC, FDA, and the ADA have issued guidance for dental offices on maintaining DUWL. It is the recommendation of these agencies that waterlines are to be treated with a disinfectant/chemical and then monitored (tested) to ensure the water quality meets the EPA safe drinking water standards of less than 500 colony forming units per milliliter of water.

Many dental settings use water from the municipal water supply through office plumbing. Dental units carry the water through the thin plastic tubing (hoses) to the air/water syringe, handpieces, and ultrasonic scalers to the patient’s mouth. The inside of this tubing can become colonized with microorganisms called biofilm. These microorganisms can include bacteria, fungi, and protozoa.   Biofilm can form in any water environment. The biofilm must be treated with a chemical disinfectant to be destroyed, making the water safe to deliver to patients.

There are several ways to treat biofilm. Contact the manufacturer of your dental units to find out which method(s) of treatment would work best for your dental unit. They may recommend a self-contained water system, an in-line filter, or a combination of these. Self-contained water systems are used with shock treatment, tablets, or straws with either distilled or potable water. Utilizing distilled or potable water alone in the self-contained system is not enough. The water must be treated to ensure safe drinking water standards are met. In-line filters have disinfectants in the filters to control the biofilm; thus, delivering safe water to patients.

Outbreaks of illness have occurred due to untreated DUWL, including one case in Georgia and another in California where pediatric dental patients developed Mycobacterium abscessus after treatment in pediatric dental practices. The infections required hospitalization of several children ranging in age from 4-8 years old. The infections were linked to the untreated contaminated water from dental units. Treatments varied from IV antibiotics to surgery for some of the cases.

Once you have determined the DUWL treatment that is best for your facility, the CDC recommends that you consult with the manufacturer on the frequency of monitoring (testing). However, even if the manufacturer does not recommend routine monitoring, the CDC does recommend routine monitoring. Monitoring dental unit water quality helps identify any problems in performance or adherence with maintenance protocols. It also provides documentation of compliance. Monitoring is the only way to ensure your product is working for you and that safe drinking water standards are met. OSAP recommends that testing of DUWL be done at least quarterly. ADA also recommends routine monitoring of DUWL. If the manufacturer issues no guidance for monitoring, the facility should monitor (test) on a routine basis. TMC recommends using the strictest standards, which is OSAP’s at least quarterly recommendation.

Testing of DUWL can be performed by using commercial self-contained test kits or commercial water-testing laboratories. If your water quality doesn’t meet drinking water standards, actions should take place to correct the issue. Those actions could include a shock treatment followed by treatment (straws, tablet, in-line filter) and then re-testing immediately after treatment. However, always consult with the manufacturer of the product or dental equipment for guidance.

Dental unit water that is not treated is likely to contain high numbers of microorganisms and most likely will not meet drinking water standards. Not treating DUWL is inconsistent with accepted infection control principles. Dental facilities should work with equipment manufacturers to ensure their water treatment meets or exceeds the standards set by the EPA for safe drinking water.