Heating and Ventilating

 

A balancing act for commercial buildings

Throughout 2020 public buildings have seen unprecedented periods of closure; however, many may not realise how these closures could impact the operation of buildings

Whilst buildings have remained empty, the water and HVAC systems within offices and other public buildings have been largely unused which poses additional risks for public health, through diseases such as Legionnaires. 

Legionnaires Disease is a lung infection caused by the bacterium named legionella pneumophila, which is commonly found in water. The recent lockdowns created an optimum environment for the bacteria to proliferate within water systems. The bacteria can exist in any water system but will specifically cause issues in man-made water systems such as large plumbing systems, showerheads, sinks and hot water tanks. Upon reopening of buildings, and without proper precautions, the bacteria-infected water in an aerosolised form can then be released into the surrounding space when the water systems are used, this can then be inhaled by those in the vicinity.  

Symptoms of Legionnaires Disease are similar to the symptoms of COVID-19, with a high temperature / fever and a cough being amongst the common symptoms for both. Whilst having similar symptoms both illnesses are transmitted in different ways and require different treatments, so it is imperative to get an accurate diagnosis from a medical professional. Legionella is not thought to be transmitted from person to person, however because of the way that the disease is spread it is not uncommon to see localised outbreaks. 

To prevent a localised outbreak of Legionnaires Disease, it is important that the water systems are adequately checked, inspected, and cleaned in line with the building’s guidelines, prior to reopening, especially systems that have not been used, as these will have been holding stagnant water for some time. Buildings that had thermostatic balancing valves (TBV) installed prior to the lockdown may have an easier task on their hands, when compared to those that did not.

Thermostatic balancing valves are designed for use in domestic hot water systems (DHWS) to accelerate hot water delivery to the tap, reduce water wastage and conserve energy, though they are now being specified in public building installations to help protect against the growth of the legionella pneumophila bacteria. 

In its optimum environment the legionella pneumophila bacteria will multiply rapidly, this usually occurs when subjected to temperatures between 32°C and 42°C. Therefore, HSE requires the temperature of stored hot water to be at least 60°C. This is where thermostatic balancing valves are required; by design they provide thermostatically controlled regulation of flow and thermal disinfection and therefore assisting with protection against legionella. Many high quality TBVs would come with an automatic legionella disinfectant feature and a temperature verification port and gauge as standard, allowing the engineers to easily follow any temperature logging procedures and alerting them to any potential issues at an early stage. 

Due to the buildings being unoccupied, there has been no demand for the water supply meaning the water within the systems will have remained stagnant throughout this period, pair this with the warm weather during summer and it has created an ideal environment for the bacteria to proliferate. 

If thermostatic balancing valves are present within the water systems, the engineers will be able to utilise the thermal disinfection function which will increase the temperature of the system to temperatures above 60°C – often to around 70°C – running the system at this temperature for a period of time will eliminate the legionella bacteria that has been able to exist. 

Whilst thermal disinfection is said to be one of the most effective and reliable ways to eliminate legionella bacteria within water systems, other options are available such as water chlorination, these may be the preferred option for those with systems without a thermostatic balancing valve installed. However, these methods do have their disadvantages, the added chemicals can affect the water quality and also cause corrosion. 

Whilst many large premises will have engineers who oversee the day-to-day maintenance and as such, will be aware of the issues that stagnant water creates and how to overcome these, the smaller premises and businesses amongst us may be facing an unprecedented challenge. However, the European Society of Clinical Microbiology and Infectious Diseases (ESGLI) has issued guidance for managing legionella in building water systems during the COVID-19 pandemic, and gives instructions on how to safely reopen these systems. 

Darren Baxter, Albion’s sales and marketing director, comments: “It is likely that many small businesses will not have engineers overseeing the maintenance of facilities on a day-to-day basis, this lack of knowledge and dedicated personnel, combined with the nature of some of these businesses, means that they could be most at risk of causing an outbreak of Legionnaires Disease. 

“For example, hairdressing salons are particularly vulnerable because of facilities in their premises such as showerheads, which is a prime outlet for dispersing the infected water. Systems can be designed in a way that can prevent the growth of bacteria, rather than having to eliminate it after it is found to be present. Whilst this can reduce the amount of intervention needed, regular checks and maintenance should still be carried out periodically, whether this is by a professional company or a competent individual depends on the business in question. As always, if in doubt, leave it to the professionals, especially when public health is on the line.”

Professionals within the building services industry would recognise the importance of preparing water systems before use, however, the average business owner is going to be focused on ensuring that social distancing can be adhered to and the correct equipment and procedures are in place, preventing further spread of COVID-19. With so many factors to consider before reopening, something that is out of sight, such as water systems, could easily be forgotten.

Mr Baxter adds: “It is looking likely that these reopening procedures could be carried out a number of times before life is back to normal, which makes it even more important to have a system that is efficient and effective. A well-designed system will not only safeguard public health, but it will also provide optimum performance and maximise energy efficiency. By incorporating valves such as the thermostatic balancing valve it reduces the need for manual intervention when it comes to reopening and reduces the risk of human error.”

Having said this, storing and circulating water at such a high temperature is not without its risks. This is where valves such as thermostatic mixing valves (TMV) are required, these valves will blend hot and cold water to achieve the pre-set delivery temperature at the outlet, providing a comfortable and safe supply for use. This is especially important on systems within healthcare premises where the individuals using the water are particularly vulnerable (young children, the elderly, and people with disabilities). On these installations it is imperative that a risk assessment is conducted to weigh up the risk of scalding and the risk of infection from waterborne pathogens, not only legionella but also others such as pseudomonas aeruginosa, stenotrophomonas maltophilia andmycobacteria. The Department of Health has issued guidance on this in their document titled - HTM 04-01.

3 February 2021

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