Monday, 28 March 2011

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.