Nuby Rapid Cool - Kettle Question

[Lcm11]

I'm using the Nuby Rapid Cool to make up formula, I'm mixing the powder and hot water together in the rapid cool (not using the hot shot method).

The instructions say we need to use 1 litre of fresh water in the kettle for every feed. Why is this? It seems like such a waste of water. If there's already cooled water in the kettle, is it really going to cause harm if I boil it again and use it?

Yes, the potential is to increase the amounts of contaminates in the water by re-using already boiled water and boiling it again. It's unlikely to actually cause any issues in the UK, but on the other hand it's very easily avoided by using fresh water each time.