If you're on chlorinated city water, you don't really need to worry about bacteria growing in the tank - that's what the chlorine is for.

The programme runs automatically and I don't think I'm able to turn it off. It runs if the temperature hasn't reached 65 degrees Celcius for 14 days. I would have preferred to be able to control how often it runs, but such is life.

Under Dutch Law chlorine is no longer allowed to be used as a primary disinfectant. The water quality probably ranks among the highest in the world, but once there is a small contamination there's not a lot to kill it off. The risk is very small, but it's about €10 to keep the water 110% safe year round; so I'm happy letting it run.