All water quality data comes from the Environment Agency and the Department for Environment Food & Rural Affairs' water quality data archive. If you have any questions about using the data, please contact us.

For each determinand, we've done some research and come up with 'safe' levels of each one. If the level for a test site is higher than this, it gets a red marker 🔴, and if it's below this point, it's green 🟢. This 'safe' level has been decided based on:

If you know of any other research, government data, or any information about water quality for swimming, drop us an email. These markers are just an indication of water quality. Take a look at this page for more information on outdoor swimming