Potable Water Testing & Vending Machine Appraisals

Public supplies of drinking water serve the majority of buildings in the UK. The range of treatment processes, which this water will have undergone, includes storage, flocculation, sedimentation, filtration and disinfection, usually with chlorine. The objective of this water treatment is to produce a final water, which is microbiologically and chemically safe for consumption, as well as aesthetically acceptable. Within a typical office building this water will be used for a variety of purposes including; making hot drinks, supply to drink vending machines, food preparation and in keeping with the emphasis on a healthier lifestyle, as cooled pure water. Additionally many buildings are nowadays equipped with bottled drinking water stations. The question remains in all of these cases, what is the quality of the water at the point of use?

Bacteriological Contamination of Drinking Water

The greatest danger associated with water intended for drinking - whether it occurs as a result of deficiencies in the supply water, as a result of the storage and distribution of the water within the building or as a consequence of pollution at point of use - is contamination by human or animal waste. This is because human or animal excrement may contain causative organisms of many communicable diseases, such as typhoid fever, bacterial or amoebic dysentery etc. In addition to the direct drinking of contaminated water, its use in the preparation of food and in applications such as vending machines, may allow the multiplication of microbial pathogens and therefore also present obvious dangers. Because they are relatively easy to isolate and characterise, and because they are always present in large numbers in the faeces of all warm blooded animals, determination of the level of certain indicative organisms is used to denote that pathogens could be present and that the supply is potentially dangerous to health. The organisms used are Escherichia Coli (E. Coli) and other coliform bacteria.

In addition to the potential to harbour pathogenic organisms, water will also contain a variety of other micro-organisms and these will have different optimum temperatures for growth. Most bacteria capable of growth in water will, on laboratory media, do so best at 22oC. However, organisms that are likely to have gained access the system from external sources may well grow best at 37oC. Since these two groups of organisms differ in their significance, it is desirable to count them separately. These so called 'colony counts' are useful for indicating the cleanliness and integrity of water systems. The main value of these colony counts, therefore, lies in comparing results of repeated samples from the same supply, thus allowing any exceptionally high levels or significant changes to be detected.

Potable Water Standards

The European Community Council Directive No. 80/778/EEC, suggests colony count 'Guide levels' for the quality of water intended for human consumption. British practice, as detailed in the Report on Public Health and Medical Subjects No. 71. The Microbiology of Water 1994 Part 1 - Drinking Water, is based upon the philosophy that significant changes in the usual counts for a given supply are far more important than the absolute numbers. Report 71 also recommends limits of; no organisms detectable for E. Coli and no more than three organisms per 100 ml for coliform bacteria. It goes on to state however, "ideally all samples taken from a distribution system including those from consumers' premises should be free from coliform organisms". HBI therefore recommends that regular, routine should be undertaken on all water sources intended for human consumption or food preparation.

A further EC Directive details 'Maximum Admissible Concentration' values for colony counts on production of bottle waters. Samples taken from point of use will obviously contain higher levels than at the source of bottling. HBI's experience with bottled drinking water supplies provided within the office environment is that they frequently become contaminated at the point of use, with a subsequent deterioration in the quality of water supplied. Clearly a regular check on the quality of these systems will assist in ensuring that cleaning routines are successful in maintaining a high quality water supply.

Drinks Vending Machines

The Automated Vending Association ("AVA") issues an Industry Guide to Good Hygiene Practice: Vending and Dispensing Guide Supplement (To the Catering Guide). The AVA Guide states that the quality of water supplied to vending machines is of paramount importance, but does not recommend any specific standards for the water supplied to machines, other than to state that the water must be potable and must not effect the wholesomeness of the finished product i.e. the vended drink. The Guide goes on to state however that water, when dispensed from a vending machine, is by definition a food. As such, the requirements which apply are those contained in the Food Safety (General Food Hygiene) Regulations 1995 and not the drinking water Regulations. HBI's vending machine inspection service includes; inspection of the cleanliness of the machine (including the condition of ingredient dispensers), a review of the siting and installation, hot vend temperature testing and testing for water quality.

Regular Monitoring

With all of the above tests it is important to realise that a single laboratory examination of any water, no matter how favourable the result, does not justify the conclusion that all is well and that the supply point will remain suitable for drinking purposes. It is essential to examine water supplies frequently and indeed it is more important to test regularly with a simple test, than occasionally with a complicated test or series of tests.

The HBI sampling protocol is designed to confirm the integrity of potable water supplies and to aid in diagnosis of contaminated systems. With virtually all modern buildings now providing potable water supplies for the occupants and increasing awareness of environmental health issues, regular, routine monitoring of potable water supplies should be considered an essential part of the routine maintenance programme for every building.