For many of us, this is one of the most memorable school science facts. Water’s made of H2O – two hydrogen atoms, one oxygen atom. That’s all it takes to make the wet stuff, right? Well, sort of. Completely pure water is composed of just two elements. In scientific terms, it’s really quite a simple substance. But not everything’s as simple as Key Stage 2 science books. In reality, water picks up much more than hydrogen and oxygen as it travels round the water cycle. Think of sea water, for example. It only takes one taste to realise the stuff’s saturated with salt, and isn’t safe to drink. But as this water evaporates into rain, and runs across the land as rivers, any salt is left behind well before it reaches our taps. But it’s not a good idea to drink river water either. As water runs across our landscapes, it picks up lots of dirt, pollutants and bacteria – so drinking it could be a quick ticket to a sick bed. In fact – it’s inadvisable to drink any water you find ‘in the wild’. The only exceptions to this rule are the rare occurrences when water is filtered naturally through a spring. Springs need a very specific set of circumstances to produce clean, drinkable water. If the rocks that make up the spring aren’t right, or the water’s polluted before it enters the system, then the water will end up less-than drinkable. So even if you know a body of water comes from a spring, it’s always best to assume it’s undrinkable anyway. But there is a way to get tasty spring-style water at work – a mains-fed water cooler with a filter. Filters remove the stuff which gives water that ‘tap water’ taste, so you end up with beautifully clear water that tastes totally natural.