woman drinking water

Every glass of tap water you drink has been through 10 people before you

Is it true to say that every glass of tap water you drink has already been consumed by up to ten people before you? Well, it might be a horrid thought but we are here to clarify the facts around the matter.

Water is finite

Scientists believe that the water on Earth is the same water that’s been here for nearly five billion years. Water is finite: the amount of water on our planet – whether fresh, salty, frozen or underground – has always been and always will be the same. In other words, the amount of freshwater that is available for human consumption might change but the amount of water never has and never will. So, what we use now was used by the dinosaurs.

Water is a pure substance, a colorless, odorless tasteless liquid. Thanks to grade school science we all know that it’s comprised of three atoms— two hydrogens and one oxygen. One of the most important properties of water is that it is a solvent – it is good at dissolving substances. Because of this, water is hardly ever found in its pure form. 

How we deal with water on earth

The water we use on Earth is dealt with and recycled in two different ways. Firstly, wastewater that has been used in homes, offices, and factories is transported to water treatment plants where it is purified before it makes its way back to where it is reused. In other words, this used water is filtered so that the water that comes out of our taps is free from harmful bacteria and safe to drink. But, purified or not, it’s the same water that has always existed on Earth.

Secondly, stormwater collects when rain falls on roofs, roads, and other land areas. It is carried away in stormwater drains and released into rivers, lakes, or the ocean. As it heats up, the water evaporates (turns into water vapor) and forms clouds. The clouds cool and the water falls as rain, snow, sleet, or hail. When it reaches the ground, the cycle continues. Even water that doesn’t flow into oceans, lakes, or rivers is recycled. It sinks into the earth and is either absorbed by plants or flows into underground aquifers. Water from both of these cycles can and will find its way into your glass.

Tap water ratio

Believe it or not, people have actually calculated how much-recycled urine finds its way into our tap water. In an article in Core Economics, Paul Frijters maintains that, “The urine ration is 350 million years of 5 billion ton of wet vertebrates urinating eight times their body weight per year equals 14,000 million cubic miles of urine. Which means the atoms in your average water molecule will have been concentrated urine some 10 times already.”

The formula he used to calculate this is not simple. It goes: 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).

What’s more, he believes this is a conservative estimate. Luckily, however, we know what makes water unsuitable and we can test it before it is allowed into the system. There is advanced technology that enables us to separate the waste from the water including different types of filtration and reverse osmosis.

Ultimately, you don’t have to worry about water that was once part of urine, or that it’s ‘been through 10 people before you.’ No matter how many people it has passed through, by the time we drink it, it should b clean! But it’s nice to have some perspective, isn’t it?

Keep Reading: Researchers Successfully Prove Teleportation Is Possible


  1. How every glass of tap water you drink has been consumed by up to TEN people before you.Daily Mail. Stacie Liberatore. November 1, 2022.
  2. Every glass of tap water you drink has been drank by ten people before you.Lad Bible. Claire Reid. November 2, 2022.