CPD Legionella The prospect of a Legionella outbreak is a constant concern. Legionella is a bacterium that causes Legionnaires disease, a potentially fatal form of pneumonia. Legionella bacteria are common in natural water sources but conditions are rarely conducive to people catching the disease. This can occur in purpose-built water systems. The risk of exposure to Legionella increases in warm water, passed to humans breathing in aerosollike droplets of water. Guidance for the control of L pneumophila in water systems is provided in the Health and Safety Executive Approved Code of Practice (ACOPL8) and its associated regulations, HSG274 Part 2. Certain conditions support growth of bacteria, temperatures at a range of 25C 45C, as well as deposits such as lime-scale, rust, sludge and organic matter. Therefore, it is important to control the risk by introducing measures that restrict the growth of bacteria. This is achieved through temperature control, maintaining stored water at least 60C and ensuring distributed water is supplied with 50C water (55C for healthcare) within 1 minute. According to the ACOP L8 guidelines, continuous ow direct to outlet systems are low risk for Legionella, due to it allowing for a full turn-over of water volume, AND no stored water and accurate temperature control. However, this can be further reduced by implementing more preventative measures which include: s OOD SYSTEM DESIGN THAT HAS GOOD MOVEMENTTURNOVER AND TEMPERATURE CONTROL helping to avoid encouraging legionella growth. s !VOIDING DEAD LEGS CAPPED ENDS s +EEPING PIPEWORK AS SHORT AND DIRECT ENSURING ADEQUATE INSULATION s -AINTAINING CLEANLINESS OF SYSTEM n HARD WATER AREAS SHOULD BE TREATED n SO SCALE is reduced using measures such as a zinc anode or a copper and silver ionization stagnant water. s %NSURING COLD WATER COMES FROM WHOLESOME MAINS At present, two of the main forms of supplying DHW are continuous ow (instantaneous) water heaters and more conventionally, storage tank water heaters. Both have their features and benets with the main differences outlined below. Storage tank water heaters: s (EAVY AND DIFlCULT TO HANDLE REQUIRING MORE MANPOWER OR MACHINERY TO INSTALLREMOVE which increases costs and consumption. s 2EQUIRES LARGE FOOTPRINT FOR APPLIANCE AND CLEARANCES s &INITE STORE OF WATER THOUGH CAN CATER FOR DEMAND SPIKES s 3TANDING LOSSES THAT INCREASE CONSUMPTION Continuous ow heaters: s s s s s s For more details on RINNAI products visit www.rinnaiuk.com !LLOWS MODULATION MORE ENERGY EFlCIENT ESPECIALLY CONDENSING VERSIONS 7ATER ONLY HEATED AND PROVIDED UPON DEMAND ELIMINATING WASTED ENERGY ,IGHT AND REQUIRES LESS TIME MANPOWER AND EQUIPMENT TO INSTALL #OMPACT IN SIZE SAVING VALUABLE SPACE %NDLESS SUPPLY OF HOT WATER !DVANCED MODELS SUPPLY PRECISE TEMPERATURE ACCURATE HOT WATER Storage tank water heaters left unmaintained can be breeding grounds for bacteria. This is one reason why they are not deemed low risk, according to the Health & Safety Executive HSG274 Part 2 guidelines, an example of a low-risk system is: where hot water is fed from instantaneous heaters or low storage volume water heaters (supplying outlets at 50 C). (Health & Safety Executive, 2014) Table 1 below shows a comparative analysis between a storage tank water heater and a continuous ow water heater. The data suggests the storage tank option is less efcient and consumes more energy, largely due to storage and pipework losses. Once the total cost is added up a continuous ow heater is the more cost and energy efcient option as well as reducing carbon emissions. 52 April 2021 www.cibsejournal.com Advertisement Feature p51-54.CIBSEMagApr21.indd 52 23/03/2021 12:07