A recent outbreak of legionella disease at the Wesley hospital Brisbane has again brought forward the link between water storage heaters and this potentially deadly virus. From the current available information, the outbreak originated from the hot water supply and has so far claimed one life with others in potential danger. Legionella is most typically found through industrial scale air conditioning units. It is in fact, very rare for a hot water supply to be the cause of an outbreak. The reason for this, is that there are strict safety rules for all hot water manufacturers to follow that prevent the growth of bacteria in the systems. The alleged outbreak was caused by an energy saving decision made by the hospital. The hot water systems had been turned down to 50 degree Celsius to save on energy and running costs.
Legionella bacteria cannot grow or survive in water that is stored above 50 degrees. As part of the safety compliance for all water heaters, the manufacturers must demonstrate that the water stored will, on a daily or weekly basis be heated to a temperature that guarantees complete sterilization. The serialization point set by the standards is typically 60 degree Celsius and at least 45% of the stored water must reach this temperature daily or 90% must reach this temperature weekly.
As most Hydrotherm owners will be aware the stored water temperature is displayed on the control panel. The temperature shown on the display is not an average but is linked to a specific sensor placed ¾ of the way down the water tank. This means that when the cut off temperature of 60 degrees Celsius is reached, at least 75% of the stored water will be 60 degrees Celsius or above.
However, please be aware that due to the legislation all hot water systems must be installed with a tempering valve. Therefore the maximum temperature that can be withdrawn from the tank is set at 50 degree Celsius. It is important to realize that although the water temperature at the sink isn’t scolding the temperature in the tank is 10 degrees hotter.
There is no need to panic, if you have any concerns then please do not hesitate to contact us and we can talk you through any questions you may have.
All our Hydrotherm models comply with the Australian Water Mark Certification Scheme. Our certificate number is W50009.
By Simon Baird