Microbore tubing can be a source of microbial contamination in mains-fed water dispensers. Frequently used dispensers normally do not have any problems because the water in the microbore is displaced frequently. It is better to have only short lengths of microbore feed whenever this is possible, for example, less than 2m. However, sometimes this is not possible and microbore tubing lengths in excess of 20m can be found in some locations.
This is not necessarily a problem, provided the dispenser is used often and the microbore in not in a warm environment (greater than 21 degrees C). Problems have been seen with only short lengths of microbore tubing when dispenser usage is infrequent, for example, in a meeting room environment where meeetings are infrequent and tea and coffee are readily available, the water dispenser may not be used for days at a time, and not used at all at the weekends.
When water is sitting in a microbore for days, the chlorination protection will dissipate and any surviving bacteria will begin to multiply, forming a biofilm in the ideal conditions of warmth and with a polyethylene substrate. A great lover of biofilms is Ps. aeruginosa and this bacterium will rapidly assist in the formation of the polysaccharide-rich film. The biofilm sheds bacteria consistently, contaminating the cooler, despite repeated sanitisation.
Therefore, when surveying locations for coolers, always try to obtain an idea of frequency of use. It may even be more appropriate to install a bottled water cooler. However, if a mains-fed cooler is installed under conditions where use is limited, always dispense at least 1 litre of water every Monday morning and consider replacing the microbore tubing every 6 months or at least every year.