Mains-Fed Water Coolers, Links with Contamination

A recent project involved a survey of mains-fed water coolers at 8 different sites, with a wide variety of installations, cooler specifications and use profiles.  Water sampling and swabbing of tap outlets at weekly intervals revealed the following summary results:

 1. All coolers had considerable bacterial loading in the tap outlets. The bio-loading increased as the frequency of use increased.

2. A large number of cooler outlets had TVC values at 72hrs/22°C too numerous to count.

3. A total of 6% of tap outlets were colonised with Ps. aeruginosa at the time of sampling. The presence of this pathogen was linked to very high use frequency, an unclean environment around the cooler and high temperatures arising from incorrect routing of pipework near heat sources.

4. There appeared no relation of contamination with length of microbore tubing or specification of the cooler, although fountains appeared more susceptible to biofilm formation than other types of dispensing coolers.

5. There appeared no difference between coolers with UV lamps and those without.

6. The hygiene awareness of the users plays an important role in reducing tap outlet contamination.

7. Of the 160 samples of water, only 3 showed coliform presence, of which 1 showed the presence of E. coli. This contamination arose from the tap outlets on the dates of sampling and was not detected in subsequent visits.

8. Many taps were encrusted with scale, indicating that they had not been changed or cleaned up during servicing.

9. Bio-loading in taps was evident within a few days after servicing.

10. The majority of coolers had no servicing docket, indicating date of servicing or verification that the servicing checklist has been completed.

A more detailed report will be made available shortly, which includes recommendations for best practice.  This work was commissioned by the British Water Cooler Association, whose members provide both bottled water and mains-fed water coolers.

Chlorine Dioxide - Disinfection of Bottling Plants

Chlorine dioxide is not new for disinfection.  It has been used for many years in water treatment and in the brewing industry for disinfecting pipelines by CIP.  Application in the bottled water industry has been overlooked.  There could be several reasons for that, for example cost were high at one time and special equipment was required to generate the chlorine dioxide gas safely.

Things have changed and it is now possible to generate chlorine dioxide for application as a CIP disinfectant very easily and often manually.  Chlorine dioxide is a gas, which will dissolve in water to produce a strongly oxidising disinfectant.  The gas can be very unstable and will break down quickly unless stabilised by careful pH control.  It has considerable advantages over chlorine-based disinfectants and does not form halomethanes or ketones if in contact with residual organic material.  If formed, these materials impart a very strong medicinal taste to water.

Chlorine dioxide is formed by the reaction of sodium chlorite solution with an acid.  In the bottled water industry, citric acid is the preferred acid.  The gas is generated and dissolves in water.  The amount of water added determines the final concentration of the product.  Chlorine dioxide is particularly good at destroying biofilm in pipework and is to be preferred over peracetic acid for this task.

The basic components required to form chlorine dioxide are available from Food Hygiene Technologies Ltd along with easy-to-follow use instructions.

Titrations to determine bottle wash detergent or peracetic acid concentration can be complicated and some involve at least three reagents. However, new drop-test kits and test strips are available that make the whole process much easier.


Using ozonation as a final terminal disinfection in bottle washing can be effective, but only if used at the correct concentration. 0.4mg/l is not sufficient and concentrations of 0.8mg/l are required for effective disinfection. 0.4mg/l will disinfect the rinse water, but not the bottle surfaces.

Only certain treatments are allowed for natural mineral water and spring water. Natural mineral water ideally should receive no treatment at all. Make sure that your labelling complies with the regulations.

Reducing greening of bottles is possible by correct choice of bottle wash detergent. The best option is to use a detergent containing a disinfectant component and wash at temperatures above 60°C. Alternatively, pre-washing equipment and chemicals are available to handle this problem.

Is your Colilert® test working? Some conditions can give false positives.

Hydrogen peroxide disinfectants are ideal for use in the bottling plant and for cooler servicing because there are no taint problems and no residuals.

ATP meters have become smaller, more robust and distinctly more affordable. Measuring points include taps, reservoirs and drip trays.