There is growing public concern about the frequency with which water companies are discharging sewage from the drainage network into rivers and the sea. Part of the problem is that when heavy rain falls, our ageing sewage system is overwhelmed. Raw sewage is then discharged into our natural water courses, causing pollution that places the health of both people and ecosystems at risk.

This animation from Susdrain explains the problem - and some solutions.

By holding back 7 mm of rain in a 210 litre water butt, we can potentially reduce the flow of rainwater into the sewage network, and consequently decrease the number of times when the sewers get overwhelmed, leading to sewage overflows.