Storm overflow register · 2025 annual return

Thames Water storm overflows, 2025

Thames Water reported 581 storm overflows in England for 2025. Together they recorded 9,189 spills over 107,822 hours, an average of 15.8 spills per overflow against 20.4 across England. That ranks 3 of 10 companies, where 1 is the fewest spills per overflow. Counting the same overflows in both years, spills were down 60% on 2024.

135 overflows did not spill · 28 spilled more than 60 times · 548 had monitors working for 90% of the year or more · 233 sewage treatment works with overflows

Hours spilling by month, 2025

Hours spilling, all Thames Water overflows, from the start/stop records. Spills running across a month end are split between the months.

All Thames Water storm overflows

Sorted by hours spilling. Open an overflow for its permit, location, reasons for high spills and improvement status.

Overflow	Discharges to	Spills 2025	Hours 2025	Spills vs 2024	Monitor uptime
Reading, Blakes Lock Storm discharge at pumping station Company site name Blakes Lock (Reading) SPS EA ID / permit TWL00344 · TEMP.1768 Outlet location SU7270073400 (OS grid reference) · View on Apple Maps WFD catchment Lower Kennet (Sheffield Bottom to Reading) (GB106039023140) 2024 spills / hours 3 / 40 Long-term average 0.4 spills a year (monitored since 2018) Monitor below 90% Comms failure / issue · Resolved - Sep Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Holly Brook	0	0.0	down 100%	89%
Reading, Caversham Storm discharge at pumping station Company site name Caversham (Reading) SPS EA ID / permit TWL00345 · TEMP.1769 Outlet location SU7280074500 (OS grid reference) · View on Apple Maps WFD catchment Thames Wallingford to Caversham (GB106039030331) 2024 spills / hours 0 / 0.0 Long-term average 0.5 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Thames	0	0.0	no change	91%
Regent Street CSO Overflow on sewer network Company site name Regent street EA ID / permit TWL00346 · CSAB.0570 Outlet location TQ3040080210 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 13 / 28 Long-term average 9.2 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	R.Thames ( Tidal )	0	0.0	down 100%	97%
Road A217, Burgh Heath Overflow on sewer network Company site name Road A217, burgh heath EA ID / permit TWL00351 · TEMP.2870 Outlet location TQ2415057390 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 0 / 0.0 Long-term average 0.9 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Watercourse/soakaway	0	0.0	no change	100%
Road A3 CSO Overflow on sewer network Company site name Road A3, roehampton vale EA ID / permit TWL00352 · TEMP.2871 Outlet location TQ2147072330 (OS grid reference) · View on Apple Maps WFD catchment Beverley Brook (Motspur Park to Thames) and Pyl Brook at West Barnes (GB106039022850) 2024 spills / hours 2 / 3.0 Long-term average 60.0 spills a year (monitored since 2019) Monitor below 90% Comms failure / issue · Resolved - Sep Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Beverley Brook	0	0.0	down 100%	89%
Roding Valley Storm discharge at pumping station Company site name Roding Valley (Ilford) SPS EA ID / permit TWL00353 · TEMP.1814 Outlet location TQ4350086000 (OS grid reference) · View on Apple Maps WFD catchment Seven Kings Water (GB106037028170) 2024 spills / hours 1 / 0.5 Long-term average 1.2 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Roding	0	0.0	down 100%	100%
Shamley Green (Wonersh) WwTW Storm tank at sewage works Sewage works Shamley Green Company site name Shamley Green STW EA ID / permit TWL00365 · TEMP.2886 Outlet location TQ0202043800 (OS grid reference) · View on Apple Maps WFD catchment Cranleigh Waters (GB106039017810) 2024 spills / hours 0 / 0.0 Long-term average 6.6 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Cranleigh Waters	0	0.0	no change	100%
Smith Street Sr CSO Overflow on sewer network Company site name Chelsea, london, sw10 EA ID / permit TWL00087 · CSSA.0403 Outlet location TQ2810677796 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 1 / 6.8 Long-term average 2.0 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Thames Tidal	0	0.0	down 100%	100%
Sonning Common Storm tank at sewage works Sewage works Sonning Common Company site name Sonning Common STW EA ID / permit TWL00374 · TEMP.2897 Outlet location SU7170079400 (OS grid reference) · View on Apple Maps WFD catchment South-West Chilterns Chalk (GB40601G601100) 2024 spills / hours 2 / 2.3 Long-term average 1.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Into Land	0	0.0	down 100%	100%
South Ealing Road, W5 Storm discharge at pumping station Company site name South Ealing Road (South Ealing) SPS EA ID / permit TWL00376 · TEMP.1929 Outlet location TQ1800079000 (OS grid reference) · View on Apple Maps WFD catchment Lower Brent (GB106039023590) 2024 spills / hours 3 / 3.9 Long-term average 2.0 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	River Brent	0	0.0	down 100%	100%
South West Sr CSO Overflow on sewer network Company site name Sw storm relief sewer, london EA ID / permit TWL00400 · CSAB.0556 Outlet location TQ2955077720 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 38 / 410 Long-term average 39.3 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	R.Thames ( Tidal )	0	0.0	down 100%	100%
Stanton Fitzwarren STW Storm discharge at pumping station Company site name Stanton Fitzwarren SPS EA ID / permit TWL00723 · CSAC.0876 Outlet location SU1746090680 (OS grid reference) · View on Apple Maps WFD catchment Bydemill Brook (Source to Thames) (GB106039023710) 2024 spills / hours 20 / 32 Long-term average 10.3 spills a year (monitored since 2023) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Trib of Bydemill Brook/Land	0	0.0	down 100%	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief C EA ID / permit TWL00731 · TEMP.2921 Outlet location TQ2906070410 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 1 / 2.0 Long-term average 14.8 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Graveney	0	0.0	down 100%	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief D EA ID / permit TWL00732 · TEMP.2921 Outlet location TQ2906070410 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 1 / 0.8 Long-term average 14.8 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Graveney	0	0.0	down 100%	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief G EA ID / permit TWL00734 · TEMP.2921 Outlet location TQ2906070410 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 0 / 0.0 Long-term average 14.7 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Graveney	0	0.0	no change	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief F EA ID / permit TWL00395 · TEMP.2921 Outlet location TQ2906070410 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 0 / 0.0 Long-term average 14.7 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Graveney	0	0.0	no change	100%
Streatham Storm Relief Overflow on sewer network Company site name Leverson Street EA ID / permit TWL00634 · TEMP.2921 Outlet location TQ2906870413 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 2 / 1.1 Long-term average 0.7 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Graveney	0	0.0	down 100%	100%
Sudbury Heights Ave, Allendale Road Overflow on sewer network Company site name Sudbury heights ave, allendale road EA ID / permit TWL00398 · TEMP.2944 Outlet location TQ1665084970 (OS grid reference) · View on Apple Maps WFD catchment Lower Brent (GB106039023590) 2024 spills / hours 0 / 0.0 Long-term average 0.6 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Wembley Brook	0	0.0	no change	100%
Sunnyside Road Overflow on sewer network Company site name Sunnyside road EA ID / permit TWL00399 · TEMP.2946 Outlet location TQ4464085830 (OS grid reference) · View on Apple Maps WFD catchment Seven Kings Water (GB106037028170) 2024 spills / hours 0 / 0.0 Long-term average 0.3 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Loxford Water	0	0.0	no change	100%
Takeley - Garnets Storm discharge at pumping station Company site name Garnetts (Bishops Stortford) SPS EA ID / permit TWL00405 · TEMP.2042 Outlet location TL5580021600 (OS grid reference) · View on Apple Maps WFD catchment Pincey Brook (GB106038033380) 2024 spills / hours 1 / 1.3 Long-term average 2.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Wayletts Ditch	0	0.0	down 100%	100%
The Broadway Overflow on sewer network Company site name The broadway XX EA ID / permit TWL00410 · CANM.0716 Outlet location TQ4153091020 (OS grid reference) · View on Apple Maps WFD catchment Lower Roding (Loughton to Thames) (GB106037028181) 2024 spills / hours 1 / 1.0 Long-term average 1.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	To the River Roding	0	0.0	down 100%	100%
Tring (2m - Main Outfall) Storm tank at sewage works Sewage works Tring Company site name Tring STW EA ID / permit TWL00416 · TEMP.2961 Outlet location SP9240013200 (OS grid reference) · View on Apple Maps WFD catchment Grand Union Canal, Tring summit (GB70610182) 2024 spills / hours 2 / 6.5 Long-term average 1.0 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Into Guc/reservoir	0	0.0	down 100%	91%
Trumps Green Storm discharge at pumping station Company site name Trumps Green Road (Virginia Water) SPS EA ID / permit TWL00418 · TEMP.2126 Outlet location SP9590010100 (OS grid reference) · View on Apple Maps WFD catchment Bulbourne (GB106039029890) 2024 spills / hours 5 / 22 Long-term average 0.8 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	River Bulborne	0	0.0	down 100%	100%
Water End Storm discharge at pumping station Company site name Water End (Newnham) SPS EA ID / permit TWL00431 · TEMP.2184 Outlet location SU6940053300 (OS grid reference) · View on Apple Maps WFD catchment Lyde (GB106039017100) 2024 spills / hours 2 / 7.5 Long-term average 9.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Lyde River	0	0.0	down 100%	100%
Watery Lane SPS Storm discharge at pumping station Company site name Watery Lane (Marsworth) SPS EA ID / permit TWL00432 · CNTM.0145 Outlet location SP9178014190 (OS grid reference) · View on Apple Maps WFD catchment Thame upstream of Aylesbury (GB106039030410) 2024 spills / hours 0 / 0.0 Long-term average 0.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Tring Bourne	0	0.0	no change	100%
West End, Essendon Storm discharge at pumping station Company site name West End (Essendon) SPS EA ID / permit TWL00436 · TEMP.2200 Outlet location TL2680008600 (OS grid reference) · View on Apple Maps WFD catchment Lee (from Luton Hoo Lakes to Hertford) (GB106038033392) 2024 spills / hours 11 / 81 Long-term average 4.7 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Wood Hill Brook	0	0.0	down 100%	100%
Weston Park CSO Overflow on sewer network Company site name Weston park EA ID / permit TWL00762 · EPRCB3293RE Outlet location TQ3200088680 (OS grid reference) · View on Apple Maps WFD catchment Lee (Tottenham Locks to Bow Locks/Three Mills Locks) (GB106038077852) 2024 spills / hours 0 / 0.0 Long-term average 0.0 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Tonebridge Brook	0	0.0	no change	100%
White Waltham Storm tank at sewage works Sewage works White Waltham Company site name White Waltham STW EA ID / permit TWL00448 · TEMP.3007 Outlet location SU8650077701 (OS grid reference) · View on Apple Maps WFD catchment Cut (Binfield to River Thames confluence) and Maidenhead Ditch (GB106039023510) 2024 spills / hours 2 / 14 Long-term average 17.4 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period	Heywood Stream	0	0.0	down 100%	100%
Wildernesse Storm discharge at pumping station Company site name Wilderness Avenue (Sevenoaks) SPS EA ID / permit TWL00765 · T02258 Outlet location TQ5400056300 (OS grid reference) · View on Apple Maps WFD catchment Upper Darent (GB106040024221) 2024 spills / hours 0 / 0.0 Long-term average 0.0 spills a year (monitored since 2023) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	Freshwater River	0	0.0	no change	100%
Combined sewer overflow at Victoria Overflow on sewer network EA ID / permit TWL00809 · EPRWB3295ES Outlet location TQ3040080150 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours – / – Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	River Thames (Esturine)	0	0.0		91%
Clapham Storm Relief Sewer Overflow on sewer network Company site name Clapham storm relief sewer, london EA ID / permit TWL00104 · CSAB.0554 Outlet location TQ3023078090 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 34 / 385 Monitor below 90% No longer operational as an overflow - permit revoked or to be revoked · Overflow no longer spilling to environment - from Jan Investigation No investigation activity in reporting period Improvement No improvement action in reporting period	R.Thames ( Tidal )	–	–		–

Sewage treatment works

Storm tanks and inlet overflows at each Thames Water sewage works. The figures are 2025 spills.

← All water companies · Contains Environment Agency data licensed under the Open Government Licence v3.0. How to read the data.