WATER HYGIENE AND SAFETY – SPECIAL REPORT


Addressing the basics of safe drinking water hygiene


Chris Rhodes, associate director, Kemper UK & Ireland, and Frank Schmidt, International Market developer, and Timo Kirchhoff, head of Product Management, at Gebr. Kemper GmbH + Co. KG in Germany, consider some of the most common challenges in maintaining healthcare water supplies at a safe temperature, and in a safe and hygienic condition, that minimises the risks of growth and proliferation of potentially hazardous waterborne pathogens in such systems. They also discuss some of the solutions to address the issue.


Stagnation is probably the most critical factor in the propagation of opportunistic pathogens. It is widely agreed, as evidenced in numerous national and international regulations (WHO, ECDC, HSE GB, ISSO NL), that the primary factor in the deterioration of water quality in buildings is the impact of stagnation. Recent studies from microbiome research suggest that just 12 hours of stagnation is sufficient to cause a significant increase in bacterial numbers.1


During periods of stagnation, prolonged contact between the drinking water and the pipework materials (pipes, valves, fittings etc) can result in a concentration of nutrients by migration from the material components into the water itself. A combination of poor material quality (e.g. materials not conforming to BS EN 164212


or WRAS regulations3 ), stagnation,


and unfavourable water quality, can promote significant biofilm development;4 within this biofilm, opportunistic pathogens – characteristically known in in international literature as OPPPs (Opportunistic Premise Plumbing Pathogens) – can multiply. Stagnation creates propagation advantages for these OPPPs, as there is no dilution or removal of the nutrients or planktonic microorganisms entering the water body. Nutrient discharge from materials in contact with drinking water must therefore be reduced by as much as is technically feasible. It is the responsibility of the designer and installer of the plumbing system that all materials are checked and approved for their ‘microbial suitability’ for the water installation in question.


The impact of temperature In addition, the impact of environmental temperature must be considered. During stagnation phases, even with standard insulation of the pipes, the temperature of the water will adapt to the temperature of the surrounding ambient air. This becomes a problem when the surrounding temperatures are in the optimal propagation range of the pathogens.


B A


Figure 1: A schematic of the operation of Kemper’s CoolFlow technology. A: KHS Coolflow coldwater cooler


B: KHS Venturi splitter valve C: KHS Coolflow coldwater regulating valve


Low temperatures provide the pathogens with poor or no growing conditions, while temperatures close to the growth optimum allow rapid growth. In the case of Legionella, atypical mycobacteria, and also Pseudomonas aeruginosa, temperature ranges between >25˚C and <55˚C, but in particular 30-42˚C, must be strictly avoided. Cold water systems can often be overlooked, and heat transfer from the ambient air to the cold water pipes can result in regular and long-lasting temperatures above 20˚C. In the German DVGW water information document number 90,5


only temperatures below


20˚C are considered safe; this correlates with many other international standards, including BS 8558,6


and HTM 04-01.7


So, alongside preventing stagnation and limiting the nutrient supply to bacteria, it is important to avoid the optimal


temperature ranges which positively condition the microbiome for the growth of OPPPs.


Influence of internal heat loads In typical pipework locations, heat from hot water pipes, heating circuits, and other heat sources such as electrical and ventilation technology, coupled with improvements in buildings’ thermal performance, can result in air temperatures significantly higher than 20˚C. The water within cold water pipework installed here, even where there is high quality insulation in accordance with BS 5422,8


can reach


ambient temperature during a short stagnation phase. Given the prevailing installation standards often present today, one can expect that following a period of stagnation, overheated cold water with temperatures much higher than 20˚C will


December 2020 Health Estate Journal 37 C


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44