Sometimes groundwater, held within rocks and soil, gets into drains and sewers. This is known as groundwater infiltration and normally happens during or after heavy or prolonged rainfall.
Most homes are connected to a public sewer in the road through private drains which carry the foul water from baths, washing machines and toilets.
When groundwater is high, it can be forced into public sewers and private drains through small cracks in pipes or inspection chambers. Over time, these small flows can inundate sewers and cause flooding.
What we are doing about it
Increasing the size of sewers is expensive and disruptive. However, we’re lining and sealing pipes across our region every day. Additionally, we use nature-based solutions such as wetlands and reedbeds where appropriate to filter groundwater.
We also monitor new housing developments to agree suitable points of connection to sewers, ensuring rainwater from roofs and driveways does not lead to infiltration.
How we protect homes and our services
When prolonged rainfall leads to exceptionally high groundwater levels, we can set up temporary pumps to remove water from sewers and discharge it into nearby watercourses. This is permitted by the Environment Agency and called an Operational Mitigation Action Plan (OMAP).
Doing this protects customers from flooding and having to restrict their toilet use. Sampling of watercourses is carried out to ensure there is no environmental impact.