Testing unit water - Capita selecta

Testing unit water - Capita selecta
Because of the obligation of the WGBO to provide safe care, it is important for oral care practices to prevent Legionella infections via the aerosol. For this it is important to have the quality of the unit water in order. The Drinking Water Act also compels the guarantee of good water quality. Finally, the Health and Safety Act also has to take this into account, because a safe and healthy workplace, ie good air quality in the practice rooms, is a legal requirement for all employees. Since Janu

Testing unit water


Because of the obligation of the WGBO to provide safe care, it is important for oral care practices to prevent Legionella infections via the aerosol. For this it is important to have the quality of the unit water in order. The Drinking Water Act also compels the guarantee of good water quality. Finally, the Health and Safety Act also has to take this into account, because a safe and healthy workplace, ie good air quality in the practice rooms, is a legal requirement for all employees. Since January 1, 2010, during official inspections regarding the unit water quality, official reports can be handed out, as well as hefty fines, when there is no testing or when there is no package of measures (management plan) in place to ensure good water quality.


Both the Infection Prevention Directive in oral care practices and the Drinking Water Act prescribe a germ count of up to 100 per ml. In other words, the water must not contain more than 100 colony forming units (cfu) per ml. That this number would be 'safe' is in fact incorrect, because it would be possible to have a number of highly pathogenic bacteria, such as Legionella pneumophila, in between. However, this number has been chosen on the basis of the cost-benefit analysis in relation to the fact that the chance of Legionella's presence increases with high germ counts. The limit for testing specifically for Legionella is set at 10,000 cfu per ml. This number must also be seen as the outcome for a workable approach and does not count as a strictly safe limit.


In order to keep the water quality in order or to get it, a number of measures are important and various factors play a role. Firstly, by means of so-called quantitative testing of the unit water, it must be demonstrated how the quality is set. This only concerns the number of CFEs and therefore not the types of micro-organisms in the water sample. No strict conditions have been set for the acceptance of these tests. Anyone can do the sampling, it does not necessarily have to be a certified person or company. Depending on the observed quality (as an indicator the germ count applies), control measures must be taken, which, if good quality is maintained, will improve and in case of insufficient quality will improve.



It is good to pay attention to some general issues that may affect the quality of the unit water:

  • The supply pipes must not run along heating pipes or be concealed together with other pipes in a cove. Also pipes that come from warm, sunny rooms are suspicious in advance.
  • No 'dead' pipes may be present in the water network of oral care practice. The standing water in such parts of the water network becomes very polluted very quickly. If there is a question from the net, the dirty water can be carried along with the running water.
  • When using separate bottles with water, taps must be tapped that flow sufficiently, because often used taps often show an extremely high germ count! Sometimes even so high that there is a contamination risk when mist is formed when the tap water flows.
  • Self-distilled water must be tapped from clean (!) Reservoirs. Mold on the inside of the tank or serious contamination of the equipment does not make much good sense about the quality of the supplied water.
  • The distillation equipment itself must also be clean and must not contain dirty filters or visible dirt.
  • Clean supply water can be obtained by placing a filter in front of the point where the water enters the unit. This technical application obviously only makes sense if the unit itself contains pipes that are each sufficiently clean.


Mold in distilled water tank


Dust in distillation equipment


Filter that purifies the supply water before it enters the unit



The pipes in the treatment unit must not be contaminated. The factors that play a role are:

  • The material of which the pipes are made is plastic, which is certainly favorable for the creation of biofilm, so unfavorable for the maintenance of good water quality.
  • The length of the water pipes differs per type of unit and can therefore give different results of testing the delivered treatment water with the same quality of the supply water.
  • Good flow is a favorable factor for maintaining good water quality. Very narrow lumens (flow-through spaces) of pipes give a low flow rate with a high chance of forming biofilm.
  • Intensive and long-term use of the unit will benefit the water quality.
  • Per unit there can be a big difference between the various connections, depending on whether the connected instrument is used a lot or a little. For example, the piping of the multi-function syringe can meet the standard, while the pipe of the green angle piece, which is used less often (and then regularly without spray cooling), appears to be seriously contaminated.
  • When working with bottles, it must be ensured that the neck of the bottle and the connecting piece do not become contaminated when changing the bottles.


Strict hygiene is required when using bottled water to prevent contamination of the unit piping


Whether the quality of the unit water is sufficient can only be made clear with water tests. These tests can easily be performed by employees of the oral care practice themselves, and dental assistants can also perform this task. Another option is to sample the samples yourself, to send the samples in a refrigerated state or have them collected by a messenger and then to have them cultivated by a specialized company. As the ultimate worry-free solution, it is also an option to outsource the sampling to a specialized company. The costs will then of course be proportionally higher.


NB It is important to engage a trusted company and always remain critical of the test results. An example is that a company was active that certified dental care practices in the area of patient safety. It also tested the water quality. A practice came through the screening well and received a certificate as a safe practice. The final report of the study stated that the available tapping points all met the quality standard for water and that there was no Legionella risk in practice. Explicitly, however, it was mentioned that assessment of the water quality of the treatment units was left out of consideration, because there was no risk of fearing...



In the following example protocol, the procedure for a so-called quantitative test is mapped step by step. According to the Infection Prevention guideline in oral care practices, this test should be performed at least every six months. In case of insufficient water quality, control measures must be taken and then must be tested until it is plausible that the water quality will remain sufficient for half a year.


Sample protocol testing unit water quality

  • Requirements: Plastic ring with 20 cm2 surface, test plates (counters), drainage devices such as special plastic tubes, pipettes or plastic cups and disposable syringes to measure 1 ml, notation system for coding the drained water, notation system for the test results.


A Instructions for use and tools for self-test water quality in oral care practices. B Set with tools for draining and breeding. Simple organization for sampling


Preferably white or in each case bright colored materials are used for tapping. When using colored cups, unwanted discoloration of the tap water may go unnoticed. Traces of oil or detergents in the tap water can also be observed and made visible with white or transparent cups.


Blue tap water by accumulating disinfectant in the biofilm



Draining in cups is much easier than using test tubes. The water jet is not always straight in the narrow lumen of such a tube and can cause tampering.


Trouble in the narrow lumen of a test tube


Mark the drain samples systematically and make corresponding culture plates.

  • Drain the water as prescribed in the instructions.
  • Pipette 1 ml from a sample, open the bract of the corresponding (!) Culture plate and carefully deposit the drop.
  • Return the top and press the drop with the plastic ring, so that the surface is exactly 20 cm2.
  • Place the inoculated culture plate in a special incubator for a prescribed period and set the correct temperature or leave the plates at room temperature for five days. As a practical solution, a (reasonably) constant cultivation temperature can be realized (which does not become too low at night or during the weekend) by placing the plates on the grid of the refrigerator.
  • Read the cultures and note that there can be big differences, ranging from 1 cfu (a speck) and countless cogs (completely pink field).


Coded drain tubes with corresponding culture plates


Drain as instructed by the manufacturer


A Pipette 1 ml from the water sample. B Deposit the sucked-up ml on the culture plate


A Close the cover sheet and press out the drop. B The surface area is now 20 cm2


A Growing plates in special incubator. B Setting the cultivation temperature for a specific period of time. C Incubate culture plates at room temperature


Strongly varying outcome from 1 to countless cfu's



If the tests indicate a too high germ count, measures must be taken. This may mean that you have to germinate more often or that even deep cleaning needs to be done.


Again it should be noted that it is not sufficient to only test the multi-function syringe, the control measures must of course be tuned to the most contaminated pipe of a unit!


After appropriate measures, such as disinfection, germination or deep cleaning, the pipes must be tested again to assess the effect. These measures with the successive tests must be repeated until the water quality (constant) is good.


It happens that a unit shows good water quality immediately after germination on the weekend, but that it will become dubious on Wednesday and even on Friday even below the norm.


It requires a lot of attention and patience to constantly bring the water quality to a good level. When this is (finally) so far, a test will be sufficient every six months.


As special points of interest the following 'water points' are mentioned:

  • The so-called standalone equipment for the mechanical removal of tartar must also be included in a management plan with regular tests.
  • Plastic reservoirs for measuring water for alginate imprints must be kept under control. Although there is no risk of nebulisation from that source, (too) high concentrations of bacteria are undesirable for material that will be processed in the mouth of a patient.
  • Eye showers in dental practice can also supply contaminated water. Extra attention is always needed for standing water. Regularly flushing the eye shower prevents it from behaving like a piece of dead lead.


A For stand-alone tartar equipment, a separate protocol with regular quality control is required. B Discolored biofilm on the inside of the water pipe by using chlorhexidine


A Contaminated reservoir of measuring bottle for water with alginate. B Thick layer of biofilm in a water reservoir measuring bottle with alginate


Incorporate eyewash regularly in rinsing protocol to prevent it from behaving like a piece of dead (water) pipe



Fixed cranes can also unexpectedly form a source of contaminated water through little use. When the bottles of a bottle unit or a reservoir of a standalone calculus unit are filled with such taps, there is certainly a risk of contamination of the atmosphere in the treatment chamber when the water is sprayed as spray cooling. Quantitative testing of fixed tapping points is therefore also recommended.


Also fixed tapping points must be tested


Water dispensers, which are currently frequently installed in waiting rooms and staff rooms, may also be a source of concern. The cooled water is supplied in clean tanks, but the pipes of the tapping installation are not cleaned when the tanks are replaced. The combination of plastic, water, room temperature or higher temperature in a sunny location or near a radiator can certainly also cause contamination of the tapping pipes, and therefore of the drinking water offered.


However, this will not entail direct Legionella risk because the water will only be drunk and will not be sprayed. The maintenance obligation of at least twice a year may seem like little when it comes to patient safety.