HOT WATER SYSTEMS
Regular maintenance and monitoring are both vital
Andrew Dabin, Product manager at Hamworthy Heating, a British commercial boiler manufacturer and supplier of heating, hot water, and renewable energy solutions, takes a look at the key considerations for designing ‘safe, reliable, and efficient’ hot water systems for healthcare facilities, and at minimising the major risk factors for the growth and proliferation of harmful waterborne bacteria within them.
A safe hot water supply is crucial, especially for healthcare premises. One of the most important concerns in this respect is the potential growth of pathogenic bacteria such as Legionella, which are especially critical for those already affected by chronic conditions and/or an impaired immune system. To mitigate the dangers involved, it is essential to consider all aspects of a hot water system – its design, the materials used, and its maintenance. In this article, we take a look at risk factors, how they are interconnected, and how they can be overcome.
Initial assessment – a water test Before the start of any ‘concrete’ planning, a water analysis (see Table 1) can provide useful information about the water quality and the likelihood of future problems in the hot water system. For instance, the harder the water, the more likely that problems associated with scale will occur. This can be problematic for the key plant and equipment, as well as impacting on the efficiency and hygiene of the system. High conductivity, chloride levels, and acidity, meanwhile, increase the risk of corrosion, while on the other hand, low conductivity can affect the performance of anodes, which are used to protect water heaters from corrosion. Additionally, water may be treated before being distributed in the cold water mains network to make it fit for human consumption. However, what is desirable for humans can damage equipment and affect its efficiency. It is necessary to take measures to prevent this.
are affected. Given the right temperature (20-45˚C), the bacterium can multiply rapidly.
Legionella bacteria are of concern, as they can cause a range of diseases, among others Pontiac or Lochgoilhead fever, and a severe form of pneumonia known as Legionnaires’ disease. While everyone can develop the disease, specific groups, and especially people with impaired immune systems and sufferers from certain chronic conditions, are particularly at risk. Healthcare facilities thus have a special duty of care to prevent the growth of Legionella in their hot water systems.
Choosing the right materials and equipment
Hamworthy’s Dorchester DR-FC Evo 30 direct-fired condensing water heaters installed at Surrey’s Molesey Community Hospital. A safe hot water system requires careful planning, and regular assessment, maintenance, and servicing.
Legionella bacteria – causes, promoters, prevention The Legionella pneumophila bacterium, albeit usually low in numbers, occurs in natural water sources. Whether the water is stagnant (lake, reservoir), or flowing (rivers, streams), does not matter; the bacterium can be present. But even man-made hot and cold water systems
Table 1. Water analysis – what does it tell me? Hardness
High Increased risk of scale build-up
Conductivity High Increased corrosion risk Low Decreased effectiveness of corrosion protection via anodes High Increased likelihood of corrosion on stainless steel Low Increased corrosion risk
Chloride pH
Acidity High 60 Health Estate Journal May 2019
A first step to hot water system design is choosing the right equipment and material based on water quality and composition to prevent problems. A water analysis – as previously outlined – can help determine the choice of materials for products and pipework, the future treatment and maintenance schedule, and whether the system is at a higher risk of breakdown due to site specifics such as hard water. In combination with this, an assessment of system design and mode of operation (e.g. what building/usage – canteen, operating theatre, or maternity ward) should be carried out to ensure efficiency and safety. All steps presented in this article are a recommendation. To ensure that particular chemicals and procedures are suitable for your equipment, always refer to the manufacturer’s instructions.
Considering bacteriological water quality – preventing biofouling Microorganisms can gather easily on rougher materials, although smooth surfaces aren’t ‘immune’ to this problem either. When this accumulation of bacteria (biofilm) gets out of hand, biofouling develops. Microorganisms feed on organic and inorganic substances contained in the water, and can multiply rapidly. For this reason, the Health and Safety Executive (HSE) recommends the use of fittings, materials, and appliances, approved by the
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