But he said “don’t use dipslides!!”

Dipslides Vs Samplers

Ring Ring….Another day, another call from a customer asking for clarification on Samplers, dipslides, Legionella and Alpron after  having a legionella risk assessment.

Let’s break this down…

Mr Risk Assessor told Sampler user “You don’t need to use those.. the HTM says they aren’t appropriate… you can’t test for legionella with those dipslides”.

Where do we start?….


Samplers…. Are they the same as Dipslides?

The answer is a resounding NO, let me explain why….

 Why are we testing?

Testing is completed for three reasons: Legal obligation, following the Alpron Protocol and Legionella risk assessment.

Legal Obligation

You test water samples from your dental unit waterline to determine whether it is of drinking quality or not. This includes whether it is at risk of harboring dangerous legionella, or pseudomonas bacteria. Note: YOU ARE NOT TESTING FOR LEGIONELLA. (This is a separate test that is done by a third party company who will take a sample and look specifically for legionella bacteria.) A higher number of bacteria within a closed water system would indicate a higher risk of legionella taking hold and endangering your patients.

This drinking quality standard is not set by the HTM01-05 but by the EU Directive 98/83 revised in June 2011 adopted by UK into its Water Supply (Water Quality) Regulations 2000. This legislation makes it a requirement for all water systems including Dental Units to be tested on a regular basis to ensure the water is safe for human consumption and meets the UK drinking quality standard. The legislation specifically states that water should be tested to measure the “effectiveness of drinking-water treatment (particularly of disinfection)”.

Alpron DUWL Protocol

As part of the Alpron protocol, we include quarterly testing to ensure your legal obligations are being met but also to prove you can continuously achieve drinking quality water using Alpron. Our own clinical research provides proof that Alpron is effective in DUWL at controlling Biofilm but users should test frequently to audit their system and maintain control of the system. Conducting this testing on a quarterly basis ensures that if there is an issue you are alerted within a reasonable amount of time. The HTM 01-05 requires the Dental Unit water to be treated to ensure biofilms are removed and safe water is produced.

Legionella Risk Assessment

Water Testing is part of the risk assessment done on all water systems at risk of harboring legionella bacteria such as Water Tanks, Air conditioning units and Dental Units. This is often done by a third party company and is conducted in a laboratory. This is one of the several tests that can be completed for the risk assessment including testing water temperatures.As previously mentioned the Sampler test is not testing for legionella specifically, rather it is giving a measure of how many unspecified bacteria are within the dental unit water sampler which can indicate an increased risk is this number is very high. Practices would review the sampler data with this in mind and could be a reason to call a third party legionella expert in or conduct a rapid legionella test to rule out legionella.

What’s the Standard in the UK?

The drinking quality standard in the UK is less than 100 c.f.u per ml of water.

A c.f.u is a Colony Forming Unit which is the unit of measurement for viable bacteria in a water sample. The standard way of testing is a laboratory based TVC (Total Viable Count) which can be done by laboratories if a water sample is sent away. This is not a cost effective or practical solution for Dentists which is why an alternative is required.

 So which test?

In order to determine if the water coming out of your Dental Unit meets the legal standard you need a test that is as accurate as a TVC but can be done and the results read in the surgery.

Currently you can choose between the QWS Sampler which is a red paddle and dark freeze dried media, or white Dipslides with pale media. There are several “Dipslides” available on the market including those referred to as “R2A” or “BT3” but it is important to understand their differences.


Both the QWS Sampler and the R2A Dipslide can be used to test water samples. Both contain the correct type of nutrients in the medium to allow the growth of micro-organisms that are viable but have been ‘stressed’. Again, both provide the nutritional support to the micro-organisms to recover and grow to form colonies that can be seen.


Other types of Dipslides currently available often use an agar called BT3 which is a general ‘all purpose’ media. This media does not contain the correct nutrients and consequently not all the viable organisms in the sample will be able grow. Use of this type of dipslide gives the user the impression that the water sample is free of bacteria. Infact the bacteria present have not been given the right conditions. This type of dipslide can give an untrue result.


As previously stated, the media used in R2A Dipslides contains the correct nutrients but unlike Dipslides the Sampler absorbs exactly 1ml of the water sample.

Remember – your testing to see how many CFU are found in 1 ml of water.

Each colony that grows on the sampler originally came from one single bacterium or colony forming unit. This means that by counting the colonies seen on the Sampler after incubation time (7 days at room temperature or 3 days at 35 degrees C ) a c.f.u number can be recorded and if this is under 100 then the water is of the correct drinking quality standard.

A Dipslide, of either type, cannot give this quantitative result because the volume of the water sample that comes into contact with the Dipslide cannot be measured.

Samplers mimic and are as accurate as TVCs  as shown in recent clinical work , first mentioned in an article in The Dentist in July 2015. This work is due for publication later this year.

In Summary

So…..Are Samplers the Same as Dipslides?  – No

Are you testing the water for legionella specifically? – No

Are you testing to assess the *risk* of legionella in your DUWL? – Yes

The HTM-01-05 says ‘ Dipslides are not appropriate’ and its right they are not! but TVCs are.

Samplers are NOT Dipslides and are as accurate as TVCs.


Use QWS Samplers to test the quality of your DUWL water and rest assured that your meeting your obligations, testing with the right equipment and seeing a true result.


And the next time Mr Risk Assessment man tells you not to use your samplers, tell him to read this 🙂




Originally posted 2016-09-22 08:24:41. Republished by Blog Post Promoter

Laura Edgar

About Laura Edgar

Managing Director of Aura Infection Control Ltd, qualified in Dental Decontamination and passionate about sharing knowledge and education. Qualified Adult training tutor and experienced in Business Management and Strategy development.