Hot water is the primary method of controlling Legionella bacteria in water distribution systems in public buildings such as swimming pools and leisure centres. The recent energy crisis has placed extraordinary pressures on budgets and economising on heating and hot water production may seem like an obvious way to reduce the energy bills. However, reducing the temperature is a false economy and places the public at risk. Carole Armstrong, marketing manager at DELABIE looks at how to keep public washrooms safe for users.
Contamination risk
Naturally present in water, Legionella bacteria develop in standing water with a source of nutrients, such as biofilm in pipes or corroded water storage tanks. They multiply at 20-45°C and are harmful if inhaled in aerosol form i.e., steam from showers.
Hot water is the typical method for controlling Legionella bacteria in non-domestic buildings. Health and Safety Guidance recommends producing and storing water above 60°C, and distributing it at 50°C. At these temperatures, 90% of the bacteria die within 2 minutes. If the temperature falls below this guideline, the risk of bacterial growth increases. Maintaining these minimum water temperatures reduces the risk of contamination and is more energy efficient than allowing water to cool during periods of inactivity then reheating.
Simple measures to help prevent heat loss and, therefore, bacterial development include keeping pipe runs to a minimum (ideally <2 metres); lagging pipes to prevent heat loss; and, where cold and hot water pipes run side by side, insulating cold water pipes to avoid heat transfer and maintain the cold water temperature below 20°C where legionella bacteria are no longer dormant.
Technical solutions against Legionella
In sports facilities, thermostatic mixing valves (TMVs) are typically used to blend incoming hot water to deliver mixed water at a safe temperature for showering. Type 3 TMVs feature a failsafe which shuts off the hot water if the cold water supply fails (and vice versa). In normal circumstances, the failsafe requires a minimum temperature differential between the incoming water supplies to ensure user safety. If this differential is not maintained, the failsafe won’t operate, putting users at risk of scalding or cold showers. With centralised TMVs there is also a risk of bacterial development. Since the hot water is pre-blended, there is no draw off from the cold supply, creating a deadleg with stagnant water. Installing showers with a point-of-use TMV avoids any upstream deadlegs, drawing from both hot and cold supplies when in use.
DELABIE’s thermostatic, electronic SPORTING 2 shower panel offers the perfect solution. When not in use, an automatic flush activates every 24 hours after the last use, running for 60 seconds and refreshing the water in the pipework and the mechanism. It is also touch-free, preventing the spread of germs by hand.
Water efficient solutions
The electronic Sporting 2 shower panel also optimises water usage. The valve closes automatically when hands are removed from the detection zone and a pre-set flow rate of six litres per minute prevents unnecessary waste. The user can therefore pre-rinse, apply the soap or shampoo, and rinse without the water running continuously. With a DELABIE electronic shower, water consumption is significantly reduced – and reducing water consumption reduces the amount of energy required to heat it.
Reducing energy costs can be achieved with compromising user safety. Legionella prevention measures must be maintained, but by reducing unnecessary water consumption, both water and energy bills can be managed in public places. By understanding the risks and installing products specifically designed to meet these challenges, the risk of contamination and scalding can be managed without blowing the budget.