Focus On: Dental Unit Waterlines

Amanda Hill, RDH, BSDH


Q: Why does biofilm grow in dental unit waterlines (DUWLs)?

A: As observed at the bottom of a periodontal pocket, biofilm loves to grow in a warm, moist environment. DUWL tubing is small in diameter and long, leaving lots of opportunity for the water and its many microbes to touch the sides of the tubing and hold on. One study shows that colony-forming units (CFUs) can grow to 200,000 in just 5 days in brand new lines. So if you’ve never treated your lines, it’s sure to be above the EPA-recommended 500 CFUs for safe drinking water.

Q: I’ve never had a patient get sick from waterlines. Do I really need to worry about my DUWLs?

A: All I can definitely say is that you don’t know if anyone you’ve treated has gotten sick, including the dental team. In Anaheim, Calif, in 2016, contaminated DUWLs sickened at least 70 children, and symptoms occurred between 1 and 409 days later. Since it was such a significant breach, doctors were able to trace the infections back to the source. Had it not been such a large population, the child that showed symptoms on day 409 most likely would have never known what caused his or her severe infection. Science is getting better at tracking the source of infections. The Anaheim case will go to trial soon and is suspected to be the biggest payout in the history of dentistry. Now is the time to get a plan into place so you can confidently respond to patients when they ask if they are at risk.

Q: So what do we have to do to get compliant?

A: First, appoint a waterline warrior, someone who will own this task and see that it is actually getting done. This does not have to be your infection control coordinator. It can be anyone in your office, but make sure he or she genuinely gets why this is important. Otherwise, it’s just another task that doesn’t get done.

Here are the 5 steps you need to take to get in line:

1. Shock. If you’ve never done this before, or are changing waterline treatment products, you need to shock your waterlines. There are many disinfectant products on the market designed to be just the strength you need to bust through the biofilm that has formed in that tiny tubing. Make sure you shock every line that water can come through, even if you don’t use it—actually, especially if you don’t use it because that’s where the biofilm is most at home: stagnant water.  

2. Test. The only way to know if your shock was shocking enough is to test the water. According to the EPA, CDC, and a whole alphabet of organizations, you need to be below 500 CFUs for safe drinking water. The Organization for Sterilization and Asepsis Prevention (OSAP) recommends you be below 200 CFUs because once you are heading north of 200, you could get to 500 by the end of the day! There are mail-in tests and in-office tests. Both are effective screening tools. If you don’t pass, go back to step one and shock again, maybe with a different shock product.

3. Treat. Once you’ve tested and documented that your lines are safe, it’s time to set up your treatment protocol to keep them that way. Much like shock products, there are many treatment products on the market. Tablets, liquids, and straws are all effective if you follow the instructions for use. Pick one product that everyone in the office understands and can stick to.

4. Maintenance. Daily maintenance is essential to ensuring a successful waterline program. Each morning, lines should be run for 1 to 2 minutes to flush out any biofilm that started forming overnight. And then each line needs to be run for 30 seconds between patients to ensure each patient is getting clean water that is free of lingering microbes.

5. Test. I know that was step No. 2, but the only way to know if your protocol is working is to test. Every product will likely fail at some point. Biofilm is a beast. OSAP recommends you retest monthly until you pass for 2 consecutive months; then you can move to quarterly testing. If a unit fails, then you start the process all over again at step 1.

Ensure you are documenting your testing because if you don’t write it down, much like on our patients’ charts, it didn’t happen! If you get a visit from your dental board or OSHA inspector, they are sure to ask to see your documentation.  

Q: The infection control program in any dental office requires a lot of time and money. How can we let patients know all that we are doing for them?

A: Celebrate your infection control program. Take pictures of your staff testing the waterlines, cleaning rooms, and running spore tests, and post passing results on social media. Start the conversation before patients even have to ask. Let them know everything you do to keep every dental visit safe.


Ms. Hill describes her career in dental hygiene as an adventure. Growing up and marrying into the military, she’s had the opportunity to experience life and dentistry all over the world. She practices part time in Virginia Beach, Va, and is an industry educator, a speaker, an award-winning author, and host of the Your Dental Top 5 podcast. She can be reached at or via email at