August 23, 2022

Complete Guide to Testing Dental Unit Waterlines

Dental assistant filling up a quickpass in-office dental waterline test kit vial with water sample

Dental unit waterline testing is the bookend of waterline maintenance. It’s necessary to perform regular testing to evaluate the effectiveness of your treatment protocol. So, whether you are just starting your dental waterline maintenance journey or want to evaluate if your current treatment is working, testing is essential to having safe water for all. Here’s what we will be unpacking in this article:

What is dental unit waterline testing?

Dental waterline testing is the process of collecting water samples from at least one waterline system and evaluating the volume of bacteria or biofilm present. The results from these tests will provide a baseline (often evaluated in colony-forming units or CFUs/mL) which will be the starting point for understanding what shock and treatment protocol is required to be compliant).

What is baseline vs routine waterline testing?

Baseline dental waterline testing refers to when a waterline test is taken before making changes to waterline maintenance protocol. This will tell you where everything stands currently and will help determine how aggressive your next steps should be.

Routine dental waterline testing is a part of consistent waterline maintenance protocol. We recommend that you test quarterly once all operatories are getting consistent, passing results.

No matter which type of testing you are doing, always be sure to document your results (which we’ll discuss more later on).

Why is testing waterlines in dental offices essential for infection prevention?

Regardless of what waterline treatment method you adopt in your practice, you are spending your resources (both time and money) to keep your patients safe from potential infections. The only way to know for certain that the time you’ve invested in waterline maintenance has led down the yellow brick road to compliance is to test your waterlines. And the only way for regulatory agencies to be certain you’ve done your due diligence is to leave a paper trail behind you in verified documentation.

It’s a bit like taking a test on the first day of a new class to see what you know (or don’t). Then, you are presented with the same test again after you’ve gone through months of diligent note-taking, lecture attendance, panic studying, and sweat-inducing pop quizzes. The only way to know if your efforts have made an impact is if there is an improvement in your results. Ideally, your results will look vastly different from the very first test to the final one.

While the process of testing can feel daunting (though a walk in the park compared to Oral Pathology), we are here to give you all the information to successfully (and regularly) test your waterlines so your office attains or maintains compliance.

How should water samples be collected for waterline testing?

The first step of collecting a water sample is to follow aseptic techniques (thoroughly washing hands, PPE, and proper handling of vials).

Once you’ve done this, there are two ways to collect water for the sample. In the past, labs and compliance agencies recommended taking a sample from each waterline. Professionals at that time thought that this will help identify the “problem” lines. While that is true, we recommend pooling your samples, that is, taking equal parts from each waterline in a single operator and mixing it in a single sample vial.

The reason is, regardless of which line failed, you will most likely re-shock all the lines in that operatory anyway. Additionally, pooling samples is a more cost and time-effective way to regularly test your waterlines.

What are the different tests available for dental unit waterlines?

There are a variety of testing options available when looking for information on the microbial count in your water. We can group them into two broad categories: In-office (in which your team performs the test) or mail-in (in which a dental water lab like ProEdge performs the test). Let’s break each category down and look at what different tests are available for your office.

What are in-office water tests for dental unit waterlines?

In-office tests are made up of three primary components: a paddle with a grid (which will display the results), a sample vial (to house the water), and germicidal neutralization (which may be included with the paddle, like QuickPass®, or may need to be added to the sample vial to ensure accurate results.

What is germicidal neutralization?

Germicidal neutralization is the process of adding germicide to the sample vial before the water is tested. It’s important to have germicidal neutralization in any in-office test because it mitigate any antimicrobial that may exist in the sample from continuous treatment products. This ensure thatactive bacteria can begin to grow large enough to be seen on the paddle after incubation. If this critical step is skipped there is a strong possibility that the antimicrobial in your treatment product will reduce or damage the bacteria cells, which may inhibit their ability to grow on the paddle. This means there is a much higher likelihood of a dental practice getting a false negative. Putting the practice and its patients at risk.

How does the in-office dental water test work?

Assuming germicidal neutralization is used, the paddle sits in the water sample briefly before being emptied (typically for 1-2 minutes) and then the paddle incubates for 48-72 hours. If your water has any presence of bacteria, visible colonies will begin to form on the paddle grid.

From here, a dental pro will take a manual count of the visible colonies with the naked eye or, in the case of QuickPass, match their paddle with a provided image. As you might imagine, this manual counting method does not always yield perfectly accurate results. In fact, with some in-office testing paddles, counting the number of colonies can be very challenging as the bacteria appear grey on a black grid. This is why QuickPass uses a specialized formula, so the bacteria appear red on a white grid. Regardless, the results from an in-office test are helpful to create a baseline so your office can take the appropriate next steps.

While the lack of exactitude may seem concerning on the surface, in-office tests are an ideal option for practices that want to test their lines regularly to ensure they are well within the range of safety. Especially for practices that follow the proven protocol of shocking, treating, and testing, in-office tests are often exactly what you need to verify that your lines continue to maintain safe water. In-office tests are also economic and shelf-stable, making it easy for offices to stock up on and have on hand to use as needed (which becomes particularly helpful in the case of a re-test).

In summary, while in-office tests may not offer the most precise bacteria count and heavily rely on your team to prefer the test accurately, they are great for offices looking for a cost-effective, convenient, and confidential testing solution. Additionally, these tests are shelf-stable, so dental offices can order in bulk to have some on hand when needed.


  • Easy to use
  • Confidential
  • No hassle to mail in
  • 48-72 hour incubation time
  • Shelf-stable
  • Cost-effective


  • Room for human error
  • Not all in-office tests are easy to read
  • Not as precise as some mail-in tests
  • Requires self-documentation

What are mail-in water tests for dental unit waterlines?

Mail-in dental water tests are collected in the dental office, tested in a water lab like ProEdge, and then verified by the lab, which results in lab-certified documentation. Here are the three most common mail-in tests:

  1. Simplate
  2. R2A
  3. Flow Cytometry

Let’s dive deeper into each of these mail-in water tests.

What is Simplate?

This test was one of the earliest innovations after the pour-plate method. In a Simplate test, the sample is collected and sent to the lab where it is plated. After a 48-hour incubation time, the lab technician shines light through the plate and counts the number of bacteria in the sample. The industry has widely moved away from Simplate with the invention of the in-office water test and the advancement of other mail-in tests. However, this is the least expensive mail-in testing option.


  • Most economical mail-in test
  • Professional technician counts bacteria


  • The least accurate mail-in test
  • Utilizes outdated technology
What is R2A?

R2A or Reasoner’s 2 Agar has long been considered the gold standard of dental water testing. R2A is another plated sample method but it utilizes agar plating that is far more accurate and consistent. This test generally has a 5–7-day incubation time and provides a specific CFU count per sample. This test is slightly more expensive than Simplate and slightly less than flow cytometry.


  • Trusted by dental professionals world-wide
  • More precise than Simplate and in-office tests
  • Advanced computer system counts bacteria


  • 5–7-day incubation period
What is flow cytometry?

Flow cytometry, or Flo™ here at ProEdge, utilizes laser technology to count the specific number of bacteria vs the number of CFUs. In flow cytometry tests, the technician applies dyes to the water sample. Different colored dyes attach to different matter within the sample. One color of dye attaches to living bacteria, another to dead bacteria, and another to damaged bacteria. The laser uses these colors to quickly identify and count each type of bacteria present in the water sample.

Flow cytometry is revolutionary in two ways: 1) there is no incubation time for the sample and can therefore yield same-day results 2) the test looks at every single bacteria cell, so the results are incredibly precise.

If your waterline protocol indicates that any failed operatory must be shut down due to a failed water test, or in the unfortunate event that your practice is shut down due to negligent documentation of water quality, flow cytometry can reduce closure times down to a single business day. Potentially saving your office upward to $15,000 a day in revenue or compliance fines.


  • Lab provides results the same day the samples are received
  • Extremely precise
  • Accounts for all bacteria present in the water sample
  • No incubation time required
  • Advanced laboratory system counts bacteria


  • More costly than other mail-in tests

Which waterline test is right for my office?

Regardless of which test a dental office chooses to use, testing is the only way to ensure your maintenance protocol is effective in achieving safe water.

We think it’s important to pause here and remember that failing a waterline test is not necessarily an indication of a lack of care by the dentist or staff. Bacteria are incredibly stubborn and require an active, aggressive waterline maintenance protocol to effectively remove bacteria from your waterline. However, the dentistry industry rarely prioritizes waterline maintenance. This is why ProEdge seeks to produce data-driven educational material, free for dental professionals so that we can become safer together.

How often do dental unit waterlines need to be tested?

If you are new to the wild world of waterline maintenance a good place to start is with regulatory agencies. The CDC, ADA , OSHA, DOH, most state dental boards, and most dental unit manufacturers are consistent in recommending that you should begin by testing monthly. It’s common for dental offices that are diving into a waterline protocol for the first to need a more aggressive regimen to remove biofilm buildup in their lines before reaching a passing result. This may mean multiple shock cycles, re-testing, or changing treatment products.

Simply put, start by testing monthly, and, once the results are consistently compliant, move to a quarterly testing cycle.

What documentation is required for waterline testing to be compliant?

As it is in the legal world: if it isn’t in writing, it didn’t happen. If there is an allegation made by a patient or staff member that a dental procedure led to infection or illness, the only way to protect your dental practice is to have proof that you’ve taken all the steps to ensure patient safety. Without proper documentation, your office’s reputation, and potentially, your license will be at risk.

In the case of waterline testing documentation, keep your results filed for at least 5 years. Be sure to develop a consistent naming system and proper labeling for all operatories. Then, if the need arises, the records will be easy to sort through. Paper storage can make this challenging, especially if the individual who manages the waterline testing changes. So, many practices have started making use of online documentation. This is ProEdge has developed a cloud-based dashboard to properly store waterline documentation across each of your operatories.

What if one (or more) waterlines fail a test?

The very first thing you want to do if your dental office has a failing waterline is to document the results. While this may not be the document you proudly hang on your breakroom fridge, it’s essential that you and any of your team dealing with waterline maintenance know which lines are failing so you can take proper documented action.

From there, we recommend you follow the 3-step proven protocol. This involves shocking your lines to break down and remove biofilm build-up, as we said before if this is your first time shocking your lines, you may need to do this step more than once. Then you can implement a treatment protocol, and the final step is to re-test. The hope is that your troubled waterline is now passing, and you can proudly document your test results.

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Publish Date:

August 23, 2022