Yes, it's a very big word for something so small, but we work hard to ensure it doesn't end up in your tap water!

Cryptosporidium is a microscopic protozoan parasite (not a bacterium or virus), which exists in the environment in a form called an oocyst. These oocysts are tiny – less than one-tenth the thickness of a human hair. The parasite is commonly found in cattle, sheep, humans and many other mammals, as well as birds, fish and reptiles.

These oocysts, if ingested, can cause a gastrointestinal illness called Cryptosporidiosis. People most commonly develop Cryptosporidiosis after coming into contact with an infected animal (including domestic pets), or an infected person, or by consuming contaminated food, milk or water. Many recent outbreaks have been associated with swimming in contaminated pools both in the UK and abroad.

We minimise the risk from Cryptosporidium by protecting our raw water sources from contamination by careful catchment management. Any Cryptosporidium oocysts which do make it into our raw water are removed by the treatment processes we use at our water treatment works.

For more information, please see our factsheet about Cryptosporidium (PDF 45 KB opens in a new window)

We also have an easy-to-read guide which explains how you can keep your tap water in tip-top condition (PDF 14.2 MB opens in a new window)

If you are at all worried about the quality of your water, please call us on 0345 672 3723. Dial 18001 first if you have hearing or speech difficulties.