Decon Pete – the importance of water quality

Decon Pete ACHWithin dentistry, water quality is an extremely important element that needs maintaining to reduce any potential pathogen risk, Pete explains

Water is used within instrument cleaning, washer disinfector fill, ultrasonic fill, manual cleaning sink fill, rinsing, dental waterlines (DUWL), autoclaves and drinking. We can sometimes overlook the necessity to maintain.

There are many different types of pathogens associated with water. The primary ones being legionella and pseudomonas.

All dental practices should have a copy of the L8 ACOP document. This describes the management of water supplies to control legionella and have an up-to-date legionella risk assessment.

UK infection control guidance documents outline: ‘The quality of DUWL output water, entering the patient’s mouth, is limited by the input water quality’.


What can affect this quality, and ultimately harbour harmful bacteria, is biofilm that can form within the DUWL tube line.

We find biofilms in many different types of systems. They are very tenacious and difficult to remove with conventional cleaners or biocides.

Biofilms form when individual bacteria, in a water line, adhere to the tube surface. When many bacteria adhere, a mechanism called quorum sensing changes the way the adhered bacteria behave. The adhered bacteria then secrete a protective polysaccharide slime, forming a continuous film.

Biofilms start to grow within slow moving or stagnant water. Hence the importance of trying to keep the water moving as much as possible.

The European standard for drinking water states that the output water must not exceed 100 colony forming units (CFU) of bacteria per ml of water. This is deemed as good, safe, quality water.

I think that it is reasonable to say that the water entering into a patient’s mouth should, at least, be in line with this European standard.

Water quality

UK dentistry guidance states that to meet the microbiological quality for output water, the input water must be below 200 CFU/ml.

To help control this, we should store water for the shortest possible time before use. We should also regularly disinfect storage containers to control biofilm.

We should also flush the DUWLs for two minutes at the start and end of the day and after any prolonged period of down time.

In addition, we should also flush for 20-30 seconds in between patients. This process will not stop the growth of biofilm; however, it will dramatically slow the growth process down by breaking the quorum sensing cycle.

It is also important that we introduce a biofilm remover to the system overnight or at weekends.

To ensure that we have good quality water and no significant biofilm issue, I would also recommend the use of a microbiological dip slide be carried out every three months. This will help to provide us with the safe knowledge that we have any biofilm issues under control.

Whichever product you chose to use to control biofilm, you should always follow the manufacturers guidance on the use and application.

There are also several specific legionella filtration units that you can retrofit to taps and treatment centres. You may also find these useful in ensuring maximum safety.

If you would like to discuss anything further, including a suggested method, then please drop me an email at [email protected] or visit

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