Wash well – and don’t forget the lid: how to clean your reusable water bottle

Regardless of the material, you must wash any water bottle regularly. Composite: The Guardian/Getty Images

Environmentally friendly and convenient, reusable water bottles are on the rise. But on social media, people seem confused about how to clean them, and post horrifying pictures of mold growing inside.

Water sourced from a municipal water supply is likely very clean, explains Kelly Reynolds at the University of Arizona, who studies water quality and disease transmission.