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Is Your Dental Operatory Water Safe to Drink?

Dental unit waterlines can harbor harmful bacteria and biofilms. Learn the essential steps to ensure your operatory water is safe for you and your patients.

In the movie Erin Brockovich, there’s a scene where the legal teams are sitting around a table, and Erin (played by Julia Roberts) says to the opposing council, “We bought that water in special for you folks; it came from a well in Hinckley,” and the lawyer that was about to drink it sets it down and abruptly ends the meeting.

I can’t help but draw a parallel from this scene to the water in your dental operatory. If someone poured you a drink straight from your air-water syringe, would you hesitate to drink it? It might look clear, smell fine, and even taste normal. But how do you know if that water is indeed safe?

Dental unit waterlines (DUWLs) are the perfect environment for bacteria and biofilms to flourish. You know how it would take forever to fill that cup from your air water syringe? That slow fill, or flow rate, gives biofilm the perfect opportunity to form in the teeny tiny porous lines in your chair. As that biofilm grows, it can then detach and end up in your patient’s mouth. And sadly, there are many cases where contaminated water has severely harmed patients. Here are the three steps to help you ensure your water is safe for both you and your patients:

  1. Shock. If all this waterline talk is new or if it’s been awhile, it’s time to shock. Shocking is the use of a strong antimicrobial to blast out the biofilm. Lots of products are available; some you leave in overnight, others are as short as 10 minutes. Read the instructions for use (IFUs) and use it properly. If you choose an overnight product, be sure to put a sign in the operatory that says “Shock in Progress.” Murphy’s law says you will be sick the next day and the temp will end up squirting shock into the first patient’s mouth!
  2. Treat. Once you have shocked, it’s time to choose a treatment product. People often wonder why you need both a shock and treatment product. I like to compare shocking to a perio maintenance visit, where you thoroughly disrupt all the biofilm. Treating, on the other hand, is akin to the self-care patients perform between visits to keep the biofilm from getting too out of control. Tablets and straws are the most commonly used products and they deliver a patient-safe low-level antimicrobial into the water, keeping the biofilm from growing too fast. Once again, read the IFUs and adhere to them.
  3. Test. The Centers for Disease Control and Prevention set the standard for safe dental water at 500 cfu/ml.1 And the only way to know if your water meets those standards is to test it. There are mail-in and chairside tests. Both have advantages. Mail-in tests give a more specific count of the biofilm growing in your lines and third-party verification that your lines are within safe standards. In comparison, chairside tests are cheaper and confidential. At a minimum, testing should occur monthly until you pass for two consecutive months and then quarterly.2 But check the IFUs for both your chair and treatment products in case they require it more often.

What If You Keep Failing?

No one likes to fail! But if you do, know you are in good company. Nearly ⅓ of treated lines still fail.3 Biofilm is a beast. We know this in our patients’ mouths; waterlines are no different. The good news is there are free resources that can help you build a successful protocol.

Call the water safety experts at ProEdge Dental Water Labs (888-843-3343 or email at No matter what product you are using, ProEdge is there to help you troubleshoot and pass the test. Then you can pour yourself a big ol’ cup of operatory water and know it’s safe. n


  1. Kohn WG, Collins AS, Cleveland JL, et al. Guidelines for infection control in dental health care Settings – 2003. MMWR Recomm Rep. 2003;52(RR-17):1-61.
  2. Mills S, Porteous N, Zawada J. Dental Unit Water quality: organization for safety, asepsis and prevention white paper and recommendations. Journal of Dental Infection Control and Safety. 2018;1(1):12-12.
  3. Molinari JA, Dewhirst N. Treating and monitoring dental water. Available at: Accessed May 13, 2024.

ProEdge Dental Water Labs

From Dimensions of Dental Hygiene. June/July 2024; 22(4):24

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