Galvanized water tanks and Legionella?

I work for an education board. We are refurbishing two toilet blocks (six sinks in each) and have discovered that the toilets are supplied off a large galvanized water tank in the roof space. The tank seems well sized and has a good through-put of water, with feed and supply to the tank on opposite ends. Does an old galvanised water tank hold any inherent dangers of Legionella?

Legionella can colonize or contaminate any water tank, including new tanks. The location of the tank (on the roof) could result in heat gain during warmer months. So despite having a cold water supply (low Legionella risk) the tank could acheive a temperature conducive to Legionella growth.

Galvanized pipes/tanks will result in higher iron in the water. Higher iron has been associated with a greater probability for Legionella.

The situation where you should be concerned about Legionella is in buildings housing individuals at risk for Legionnaires’ disease (nursing homes, hospitals, etc.). Legionella may not be a risk in your situation, but you should test the water for Legionella to provide evidence for future steps.