Sewage Overflows Near Your Property: How to Check and What It Means

In 2024, water companies in England discharged raw sewage into rivers and seas over 450,000 times, totalling more than 3.6 million hours of spills, according to Environment Agency Event Duration Monitoring data. At HouseCheckup, our £24.99 property reports include environmental risk data and proximity to waterways, helping buyers understand sewage overflow risks before committing to a purchase. The scale of the sewage crisis has made this an increasingly important factor in property buying decisions, particularly for homes near rivers, streams, and coastal areas.

What Is a Combined Sewer Overflow (CSO)?

Much of England's sewer network dates from the Victorian era and uses a combined sewer system — meaning rainwater and foul sewage (from toilets, baths, and sinks) share the same pipes. During heavy rainfall, these combined sewers can become overwhelmed. To prevent sewage backing up into homes and streets, the system includes Combined Sewer Overflows (CSOs) — overflow points that discharge excess wastewater directly into rivers, streams, or the sea.

CSOs were designed as emergency relief valves, to be used only in exceptional rainfall events. In practice, water companies have allowed them to operate routinely, even in dry weather, due to underinvestment in sewer capacity. This has caused a public and political outcry and led to significant regulatory action.

The Scale of the Problem

Data from Environment Agency Event Duration Monitoring. Not all CSOs were monitored in earlier years, so historical figures may undercount.

How Sewage Overflows Affect Property Buyers

Health Risks

Raw sewage contains harmful bacteria (E. coli, salmonella), viruses (norovirus, hepatitis A), and parasites. Properties near frequently overflowing CSOs face health risks if:

• Gardens flood with contaminated water during heavy rain
• Children or pets play near affected waterways
• The property has a private water supply drawn from a contaminated source
• Residents use nearby rivers or beaches for recreation

Environmental Impact

Sewage pollution degrades the quality of rivers and coastal waters. The presence of frequent sewage discharges near a property can affect:

• Recreational value: Rivers and beaches designated as bathing waters may lose their status
• Wildlife: Sewage depletes oxygen in water, killing fish and damaging ecosystems
• Odour: Properties near overflow points may experience unpleasant smells, particularly in warm weather
• Visual amenity: Sewage-related litter (sanitary items, wet wipes) on riverbanks and beaches

Property Value Implications

While there is limited formal research on the property value impact of sewage overflows specifically, growing public awareness is beginning to affect buying decisions. Properties marketed with river or coastal views may face increased buyer scrutiny about water quality. Areas with well-publicised sewage problems — such as parts of the South Coast — have seen buyer reluctance that could depress demand and values over time.

How to Check Sewage Overflow Risk

Several tools allow you to investigate sewage overflow activity near a property:

1. Water company storm overflow maps: All major water companies now publish near-real-time data on CSO discharges. Check your regional water company's website
2. Rivers Trust Sewage Map: The Rivers Trust provides an interactive map showing every CSO discharge point in England and Wales, with annual spill data
3. Environment Agency Event Duration Monitoring: Annual data on spill events and duration for every monitored overflow
4. Surfers Against Sewage: Real-time sewage alerts for coastal and bathing water locations
5. HouseCheckup reports: Our £24.99 reports include environmental risk data and proximity to waterways to help assess sewage-related risks

Key Questions to Ask

• How far is the nearest CSO from the property?
• How frequently does it discharge? (Check annual spill data)
• Is the property at risk of sewer flooding? (Check the water company's sewer flooding register)
• What is the bathing water quality of nearby beaches or rivers?
• Are there planned infrastructure improvements to reduce overflows?

What's Being Done About It

The government and regulators have taken several steps to address the sewage crisis:

• Environment Act 2021: Requires water companies to progressively reduce the adverse impacts of storm overflows on the environment and public health
• Storm Overflows Discharge Reduction Plan: Sets targets for water companies to eliminate ecological harm from storm overflows by 2050, with interim targets requiring significant investment
• OFWAT enforcement: The regulator has launched investigations into several water companies for potential illegal discharge, with fines of hundreds of millions of pounds imposed
• Price Review (PR24): Water companies' investment plans for 2025–2030 include billions for sewer infrastructure upgrades, though this will be funded through higher customer bills

Sewer Flooding vs Sewage Overflow

It's important to distinguish between sewage overflows (which discharge into waterways) and sewer flooding (which affects properties directly). If a property has experienced internal or external sewer flooding, this should be recorded on the water company's DG5 register. Your conveyancer should request a drainage and water search (CON29DW) that reveals whether the property is on this register.

Check Environmental Risks Before You Buy

A HouseCheckup report for just £24.99 provides environmental risk data including proximity to waterways, flood risk assessment, and local environmental factors. For properties near rivers, streams, or the coast, understanding sewage overflow risk is an increasingly important part of due diligence. At £24.99, our report gives you essential environmental intelligence alongside EPC data, planning history, and dozens of other property checks — helping you make a fully informed buying decision.