Mmmmmm….refreshing (Credit: Getty)

Health experts reckon you should be drinking between six and eight glasses of water each day.

What they don’t say is that 10 people have probably enjoyed that water before you get your lips on it.

Which makes sense when you think about it. The amount of water on Earth has stayed the same for the last five billion years.

And, obviously, water passed into the body is passed out of it again before heading off to be filtered and resupplied.

According to Economics.com, there’s actually a formula to work out how many people have sipped tap water before you. Here it is: Urine ratio = (total water urinated)/(total water) = (total vertebrate biomass ever lived* urine rate)/ (total water) = (average biomass vertebrates * urine rate per year * years of vertebrates) / (total water)

The folks that, bizarrely, worked this out assumed the urine ration is 350 million years of 5 billion tonnes of wet vertebrates urinating eight times their body weight per year, equalling 14,000 million cubic miles of urine.

‘This means the atoms in your average water molecule will have been concentrated urine some 10 times already. And that is a conservative estimate,’ the site explained in a blog post.

Well then.

This is where your wastewater gets treated so it’s good to go for another round (Credit: Shutterstock)

If you want to read the whole thing, which goes into a fair amount of detail about how much animals have urinated through the the eons, you can do so here.

Of course, this does beg the question whether or not tap water is any worse for you at all than filtered water.

Ann Bunting, a spokesperson for the Drinking Water Inspectorate (DWI), which provides ‘independent reassurance’ that the public water in England and Wales is safe and of good quality, says in no uncertain terms: ‘Drinking water quality in England and Wales is excellent, and safe to drink straight from the tap. 

‘There is no health need to drink bottled water or filtered, and the carbon footprint of tap water is many times smaller than bottled water.’

So go on, drink up. Plenty of people have before you.

MORE : Maps showing parts of UK underwater in 30 years will shock you

MORE : The best UK spas for your long-term health and wellbeing

Drink up, everyone else has.