Water Lines: Basic information to stay in compliance

January 31, 2020

Questions about testing dental waterlines are all over social and print media. Terms like DUWLs, CFUs, and LPSs are in the literature but what does that alphabet soup mean and what is a dental office supposed to do about it? The good news is, is it isn’t as hard at pronouncing words like Pseudomonas Aeruginosa (which is something could be hanging out in your dental unit waterline, DUWL, right now). So let’s get you on a path to clean waterlines and keep you off the latest news cycle.

It’s really a simple 5 step process to make sure waterlines are in the clear.

1. Shock: First you have to shock all your dental unit waterlines. When I say all, I mean ALL! Even the ones you don’t use--actually, especially the ones use--they are the most likely to have built up biofilm due to the stagnant nature of the line. You can use a diluted bleach solution or a prepared shock solution. There are many articles and videos online for the exact instructions on how to shock based on the method you choose.

2. Test: After you shock you need to determine if your lines contain less than 500 colony forming units (CFUs). There are a few options out there for testing. You can do it yourself with an in-office test such as ProEdge Dental’s QuickPass or Aquasafe water test kits. They are both easy to use. The QuickPass has a 48-72 hours incubation period, while the Aquasafe requires 7 days. Or you can outsource and send samples out to a lab. Once again, when you test you have to test ALL of your lines. So that could mean water samples from 3-7 lines per operatory--don’t forget your ultrasonic scaler, it has a waterline too. If you don’t pass the test, go back to step one and shock again.

3. Treat: Now that you have determined your lines are safe, let’s keep them that way. You can treat them daily with a tablet-like BluTab or you can install a straw into your unit water reservoir that is replaced yearly. Do not be fooled by a well-meaning rep that tells you the tabs or straw are all you need to do. Unfortunately, if you aren’t doing step four the biofilm will build right back up.

4. Maintainance: Daily maintenance is key to keeping your lines free of CFUs. At the end of each workday, the lines need to be dried so that water doesn’t sit stagnate overnight or over the weekend. Standing water is a biofilms dream. Just think of a vase of flowers, after that water sits for days a film grows on top of the water and on the sides of the vase that is hard to remove. That’s a biofilm. So imagine your tiny dental waterline tubing and water sitting in it for any period of time. Here’s an example of a daily waterline routine:


  • Fill the unit reservoir with tap water (note distilled water will not keep you safer, in fact, it has no chlorine so you are more likely to build up biofilm)
  • Put in Blu Tab if using and reattach water bottle
  • Turn unit on
  • Run all lines for at least 30 seconds

Between Patients:

  • Run all lines that enter the patient’s mouth for 20-30 seconds


  • Turn unit off
  • Drain water from the unit reservoir, dry Straw if using, and reattach bottle
  • Turn unit back on and run all the lines until they are dry
  • Turn unit off"If your ultrasonic scaler has a separate water source be sure to complete all the steps above with it."

5. Re-Test: It is key to re-test your waterlines to be sure that regrowth has not occurred. OSAP recommends that you re-test monthly at the beginning of implementing your waterline maintenance routine. If monitoring results show your water quality is acceptable for 2 consecutive months then you can move to quarterly testing. If a unit fails then you start the cycle all over again with step one and shock your lines.

It is key to also be sure you are keeping records of your efforts. Dental Board inspectors are consistently asking for this documentation to ensure you are compliant. ProEdge.com has a free handy checklist you can download (link below). Or you can create your own. Just be sure you are keeping track!

While this may seem like one more thing to add to our already busy routine it’s a key step to ensure you are providing a safe environment for your patients. I have had dentists push back at the cost of the tests or the time it takes to establish yet another protocol. But just imagine if your mother, grandmother, child or even you, were in that chair, wouldn’t you want to know those lines are safe?

- Amanda Hill, RDH, BSDH

Disclaimer: This article is the sole opinion and research of the writer and doesn't reflect the opinions of ZenSupplies.


More references on this subject: https://osapjdics.scholasticahq.com/article/5075-dental-unit-water-quality-organization-for-safety-asepsis-and-prevention-white-paper-and-recommendations-2018

Waterline testing Log: https://proedgedental.com/wp-content/uploads/2019/05/QuickPass-Log_5.2019_V3.pdf

Some of the ABBREVIATIONS as a reference:

ADA - American Dental Association

ANSI - American National Standards Institute

AWWA - American Water Works Association

CDC - Centers for Disease Control and Prevention

CFU/mL - Colony forming units per milliliter

DFU - Directions for use (see also IFU)

DHCP - Dental health-care personnel

DUWL - Dental unit waterline

EPA - US Environmental Protection Agency

FDA - US Food and Drug Administration

HAI - Healthcare-associated infections

HPC - Heterotrophic plate count

IC - Infection control (or infection prevention and control)

⬅ Back to Blog