Can water be too clean?

We all know the dangers of drinking contaminated water. And common sense says the cleaner water is, the better. But did you know that water can actually be so clean that it’s dangerous to drink?

It sounds crazy, but it’s true. UPW (ultra-pure water) – water that contains absolutely nothing except water molecules – is considered an industrial solvent. It’s certainly not suitable for drinking. And millions of gallons of this super-clean stuff are made every day, as it’s a vital part of the semiconductor manufacturing process – tech boffins use it to clean microscopic particles off computer chips.

To make the stuff, you’ve got to put ordinary drinking water through reverse osmosis machines. You might have heard of these being used in industrial water filtration processes. The process is quite complicated, so we’ll keep it simple – they make water REALLY clean.

Oh, did we forget to mention this was only the first step? To make UPW, you’ve got to filter the water 12 more times after reverse osmosis has already made it very, very pure. But why would drinking this water be bad for you?

Well, we mentioned UPW is a solvent – but so is normal, everyday tap water. Though we think of solvents as corrosive chemicals, all it means is a substance that ‘wants’ to become a solution by dissolving other materials. That’s what makes water so good at cleaning.

Once you remove these other materials from water, though, it becomes ‘hungry’ for more materials – so if you drank it, it would start leaching vital minerals from your body!

Truth be told, just the one glass wouldn’t hurt you. But it’s unlikely you’d want to drink more than a sip anyway. See, ultra-pure water tastes horrible. It turns out that cool, filtered water tastes great because it still has a few (very safe) minerals and salts in it. These are what give it its crisp, refreshing flavour.