Croydon has had some of South London's worst home flooding in recent years, and the 2025 to 2026 weather has kept that pattern going, because the borough has ridges and valleys, large areas at risk of surface water flooding, and Victorian combined sewers. Those sewers were never built for the heavy rain that now arrives more often. This post looks at why Croydon's drains struggle in heavy rain, and what homeowners have done to protect their homes.
Why Croydon Floods More Than Neighbouring Boroughs
Since several causes come together here, it helps to take them one by one.
The Wandle and its tributaries. The River Wandle runs through Croydon before it flows north through Merton and Wandsworth to the Thames. In heavy rain, it can rise fast. Streets on its flood plain then see water running over the surface, even when the drains are clear.
Surface water flood risk areas. The Environment Agency's flood maps show surface water risk across large parts of Croydon. Surface water flooding happens when rain overwhelms the drains, while the water runs over the ground instead of entering the sewers.
The combined sewer problem. Like much of south London, Croydon has mostly combined sewers, which carry foul water and rainwater in one pipe. Because of that, in heavy rain, the system fills up. Flow can then back up into streets and sometimes into homes at low points.
Clay soil and hard surfaces. South London sits largely on London Clay, which water barely passes through. Meanwhile, gardens have been paved over for parking and extensions. So more water reaches the drains, and it arrives faster.
Areas Most Affected in 2025–26
Since some parts of Croydon are more exposed than others, these areas drew the most emergency calls in the worst rainfall events.
Addiscombe and East Croydon. A brook catchment runs beneath Addiscombe, so surface water flooding recurs here. Some streets have seen water enter through basement-level drains.
South Croydon and Sanderstead. Higher ground slopes towards a nearby stream catchment. Homes at the foot of slopes get concentrated run-off in heavy rain, while culverted streams can reach capacity.
Thornton Heath. This area has one of the oldest drain networks in the borough, and its Victorian combined sewers can struggle in heavy rain. Blocked gullies make the surface water position worse, and residents often complain about them.
Shirley and the West Wickham boundary. Water from the green belt to the east runs towards low-lying residential streets in Shirley, and homes at the lowest points have flooded more than once.
What Thames Water Is Responsible For (and What It's Not)
Because many people are unsure who looks after what after a flood, here is a guide.
Thames Water looks after public sewers. If a public sewer surcharges and water enters your home, Thames Water may be liable. Report the event to Thames Water, since it logs the incident, which helps any later claim.
Croydon Council looks after highway drainage, which means gullies in the road and pavement, and watercourses that are not main rivers. Report blocked gullies to the council. For a watercourse causing flooding, contact its flood risk team.
Homeowners look after their private drains inside their boundary. If your private drain is blocked and added to the flooding, the repair is yours to arrange.
The Environment Agency looks after main rivers, while the River Wandle is a main river for most of its Croydon length.
What Homeowners Have Done to Protect Their Properties
Since floods leave lasting damage, Croydon homeowners have taken several practical steps.
Private drain inspection and clearance. Clear drains are less likely to back up in heavy flow, since water has room to move. A CCTV survey before winter finds blockages and defects before the wet season.
Non-return valves. An anti-flood valve in the drain below the lowest floor stops sewer water backing into the home, and it is one of the most cost-effective protections for homes in flood-risk areas.
Flood barriers and door guards. Some owners on the worst-hit streets have fitted removable barriers or fixed threshold barriers at ground-level doors. They work best where overland flow, not sewer backup, is the main cause, because they block water at the door.
Permeable paving. Some owners have swapped hard drives for permeable ones, such as gravel or block paving with open joints. Rain then soaks in, so less runs straight into the drains. It helps most as an area-wide measure, yet it still helps homes with large paved frontages.
Sump pumps and basement tanking. Basements in the worst-hit streets often need more than passive defences. A sump pump in a sealed chamber, with battery backup for power cuts, removes water faster than it builds up. Tanking, a waterproof layer on basement walls and floors, is the longer-term fix where groundwater keeps pressing. However, it is a big investment, and costs vary widely.
Property flood resilience grants. Some residents have applied for support through the Environment Agency and the council after major floods. Such schemes may fund measures like non-return valves, flood doors and air brick covers. Because eligibility depends on the flood event and the measures chosen, check the council's flood risk page for current details.
Emergency Drain Support in Croydon
Drainage firms face high demand during and after a flood. Because of this, it helps to know a local contractor before you need one.
Our Croydon emergency drain service deals with backed-up drains and sewage in the property. While every case differs, if your drain has backed up, request a quote online via our contact form. After a flood, you can also book a CCTV drain survey in Croydon. It shows whether the line has roots, slipped joints or a collapse. For the wider picture, see our page on Croydon drain unblocking.
FAQ
Does home insurance cover flood damage in Croydon?
Standard buildings and contents cover often includes flood damage, yet it varies a lot. Check whether your policy excludes surface water or sewer flooding. Homes in high flood-risk areas may need the government-backed Flood Re scheme, which helps make flood cover available.
Can I claim against Thames Water if their sewer surcharges into my property?
You may be able to, if a public sewer surcharge directly caused the flooding. Since evidence matters, keep all receipts, record the damage and report the event to Thames Water promptly. It has a claims process for flood damage from public sewer failure.
Is it worth getting a non-return valve fitted?
For homes in areas of known flood risk, yes. It is a cost-effective protection, so request a quote for supply and fitting. It does not stop surface water flooding from overland flow, although it does stop sewage backing up through the drain.
How do I report a blocked gully on my street in Croydon?
Report blocked highway gullies to Croydon Council through its online tool or street team. Since sewers may be involved, during or after a flood, also report to Thames Water if sewer surcharge is involved.
Can I request help in Croydon during a flood emergency?
During severe weather, demand across London can be high, so response may take longer. Request a quote online via our contact form.
Because every property is different, start with our guides to emergency drain services and domestic drain jetting advice. We also cover emergency drain services in Croydon and emergency drain services in Kingston upon Thames, so you can see how the work runs near you.
