Holidaymakers heading to British beaches and rivers were faced with a very unpleasant problem this summer – raw sewage. The sewage system usually carries rainwater and dirty wastewater from bathrooms and kitchens to treatment works but during ‘exceptional events’ such as heavy rainfall, when it is likely to be overwhelmed, raw sewage can be diverted and discharged into rivers and seas. Available data shows that in 2021, water companies released untreated sewage into waterways for 2.7m hours – with many discharge pipe monitors not working or left uninstalled. Madeleine Finlay speaks to reporter Helena Horton about why this is happening, and the damage it is doing to the environment, our health, and the UK’s seafood industry. Help support our independent journalism at theguardian.com/sciencepod