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
Cholsey WwTW Storm tank at sewage works Sewage works Cholsey Company site name Cholsey STW EA ID / permit TWL00097 · CNTW.0360 Outlet location SU5909087190 (OS grid reference) · View on Apple Maps WFD catchment Cholsey Brook and tributaries (GB106039023570) 2024 spills / hours 45 / 572 Long-term average 11.5 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 44 hours spilling →	Cholsey Brook	4	44	down 91%	99%
Hull Green (Matching) SPS Storm discharge at pumping station Company site name Hull Green (Matching) SPS EA ID / permit TWL00612 · EPRFB3198AT Outlet location TL5403010650 (OS grid reference) · View on Apple Maps WFD catchment Higher Laver Brook (GB106037033490) 2024 spills / hours 0 / 0.0 Long-term average 10.0 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 43 hours spilling →	Colville Hall Brook	3	43	up from 0	97%
Tetsworth WwTW Storm tank at sewage works Sewage works Tetsworth Company site name Tetsworth STW EA ID / permit TWL00408 · CNTD.0018 Outlet location SP6847002470 (OS grid reference) · View on Apple Maps WFD catchment Latchford Brook at Tetsworth (GB106039023830) 2024 spills / hours 30 / 295 Long-term average 19.4 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 42 hours spilling →	Latchford Brook	6	42	down 80%	100%
Bramley Storm discharge at pumping station Company site name Bramley (Guildford) SPS EA ID / permit TWL00052 · TEMP.0515 Outlet location TQ0120045000 (OS grid reference) · View on Apple Maps WFD catchment Cranleigh Waters (GB106039017810) 2024 spills / hours 30 / 177 Long-term average 17.0 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 42 hours spilling →	Hascombe Stream	12	42	down 60%	99%
Haslemere WwTW Inlet overflow at sewage works (with treatment) Sewage works Haslemere Company site name Haslemere STW CSO EA ID / permit TWL00599 · CTCR.1203 Outlet location SU8779032530 (OS grid reference) · View on Apple Maps WFD catchment South Wey (Haslemere to Bordon) (GB106039017700) Treatment Reed bed 2024 spills / hours 3 / 2.7 Long-term average 4.0 spills a year (monitored since 2023) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 41 hours spilling →	River Wey (South)	6	41	up 100%	100%
Folkestone Road Storm discharge at pumping station Company site name Folkestone Road (East Ham) SPS EA ID / permit TWL00187 · CSBC.0127 Outlet location TQ4411083190 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 23 / 112 Long-term average 18.0 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 41 hours spilling →	River Roding(Barking Creek)	11	41	down 52%	100%
Hadham Mill Storm discharge at pumping station Company site name Hadham Mill (Much Hadham) SPS EA ID / permit TWL00208 · TEMP.1074 Outlet location TL4280017800 (OS grid reference) · View on Apple Maps WFD catchment Ash (from confluence with Bury Green Brook to Lee) (GB106038033290) 2024 spills / hours 35 / 220 Long-term average 23.8 spills a year (monitored since 2020) Monitor below 90% Comms failure / issue · Resolved - Jun Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 41 hours spilling →	River Ash	4	41	down 89%	82%
West Way, Botley (Syphon) Overflow on sewer network Company site name West way, botley (syphon) EA ID / permit TWL00439 · TEMP.3035 Outlet location SP4865006240 (OS grid reference) · View on Apple Maps WFD catchment Thames (Evenlode to Thame) (GB106039030334) 2024 spills / hours 18 / 116 Long-term average 12.9 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 40 hours spilling →	Seacourt Stream	10	40	down 44%	96%
Kingthorpe Terrace Overflow on sewer network EA ID / permit TWL00625 · Permit applied for Outlet location TQ2066284898 (OS grid reference) · View on Apple Maps WFD catchment Lower Brent (GB106039023590) 2024 spills / hours 34 / 97 Long-term average 20.0 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 38 hours spilling →		16	38	down 53%	100%
Rye Meads WwTW Storm tank at sewage works Sewage works Rye Meads Company site name Rye Meads STW EA ID / permit TWL00357 · CLCR.0048 Outlet location TL3948010440 (OS grid reference) · View on Apple Maps WFD catchment Stort and Navigation, Harlow to Lee (GB106038033282) 2024 spills / hours 26 / 231 Long-term average 21.6 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 38 hours spilling →	Toll House Stream	5	38	down 81%	100%
Aldershot Town WwTW Storm tank at sewage works (with treatment) Sewage works Aldershot Town Company site name Aldershot STW EA ID / permit TWL00007 · CNTD.0073 Outlet location SU8840050500 (OS grid reference) · View on Apple Maps WFD catchment Blackwater (Aldershot to Cove Brook confluence at Hawley) (GB106039017180) Treatment Reed bed 2024 spills / hours 20 / 76 Long-term average 17.8 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 38 hours spilling →	Blackwater River	9	38	down 55%	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief E EA ID / permit TWL00733 · 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 42 / 77 Long-term average 39.7 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 38 hours spilling →	Graveney	27	38	down 36%	100%
Deadmans Bridge CSO Overflow on sewer network Company site name Deadmans bridge EA ID / permit TWL00546 · EPRCB3490VW Outlet location TQ3097092230 (OS grid reference) · View on Apple Maps WFD catchment Pymmes Brook upstream Salmon Brook confluence (GB106038027940) 2024 spills / hours 35 / 93 Long-term average 22.0 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 37 hours spilling →	Pymmes Brook	21	37	down 40%	100%
Grosvenor Ditch CSO Overflow on sewer network Company site name Low level XX, grosvenor ditch, millb EA ID / permit TWL00596 · TEMP.2752 Outlet location TQ3027078790 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 26 / 66 Long-term average 20.8 spills a year (monitored since 2022) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 37 hours spilling →	Tidal Thames	22	37	down 15%	94%
Luxborough Lane Overflow on sewer network EA ID / permit TWL00480 · Permit applied for Outlet location TQ4193792541 (OS grid reference) · View on Apple Maps WFD catchment Lower Roding (Loughton to Thames) (GB106037028181) 2024 spills / hours 16 / 239 Long-term average 9.0 spills a year (monitored since 2023) Monitor below 90% Comms failure / issue · Resolved - Dec Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 36 hours spilling →		3	36	down 81%	87%
West Putney Sr CSO Overflow on sewer network Company site name West putney S R, horne way EA ID / permit TWL00438 · TEMP.2986 Outlet location TQ2348076230 (OS grid reference) · View on Apple Maps WFD catchment THAMES UPPER (GB530603911403) 2024 spills / hours 18 / 34 Long-term average 9.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 36 hours spilling →	Tidal Thames	3	36	down 83%	100%
Waverley Lane SPS Storm discharge at pumping station Company site name Waverley Lane (Farnham) SPS EA ID / permit TWL00434 · CNTM.1423 Outlet location SU8602046020 (OS grid reference) · View on Apple Maps WFD catchment North Wey (Alton to Tilford) (GB106039017830) 2024 spills / hours 11 / 71 Long-term average 12.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 33 hours spilling →	Farnham Bourne	4	33	down 64%	100%
Low Hall Farm Storm Tanks Overflow on sewer network Company site name Low hall farm storm tanks,walthamstow EA ID / permit TWL00421 · CSBC.0084 Outlet location TQ3631088060 (OS grid reference) · View on Apple Maps WFD catchment Lee (Tottenham Locks to Bow Locks/Three Mills Locks) (GB106038077852) 2024 spills / hours 20 / 145 Long-term average 13.4 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 31 hours spilling →	Dagenham Brook	5	31	down 75%	100%
Northleach WwTW Storm tank at sewage works (with treatment) Sewage works Northleach Company site name Northleach STW EA ID / permit TWL00314 · CNTD.0012 Outlet location SP1233014320 (OS grid reference) · View on Apple Maps WFD catchment Leach (Source to Thames) (GB106039030040) Treatment Reed bed 2024 spills / hours 11 / 60 Long-term average 11.4 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 31 hours spilling →	River Leach	5	31	down 55%	100%
Lindsay Drive, Falcon Way Overflow on sewer network Company site name Lindsay drive, falcon way EA ID / permit TWL00267 · TEMP.2739 Outlet location TQ1938088360 (OS grid reference) · View on Apple Maps WFD catchment Wealdstone Brook (GB106039022940) 2024 spills / hours 31 / 63 Long-term average 33.1 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 30 hours spilling →	Wealdstone Brook	20	30	down 35%	96%
Salfords Sewage Pumping Station Storm discharge at pumping station Company site name Salfords SPS EA ID / permit TWL00358 · CNTW.0279 Outlet location TQ2808046650 (OS grid reference) · View on Apple Maps WFD catchment Salfords Stream (Salfords to River Mole confluence) (GB106039017540) 2024 spills / hours 8 / 36 Long-term average 4.9 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 30 hours spilling →	Salfords Stream	7	30	down 13%	100%
Heathwall PS CSO Storm discharge at pumping station Company site name Heathwall (Nine Elms) SPS & Storm SPS EA ID / permit TWL00220 · CSAB.0522 Outlet location TQ2953077720 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 39 / 137 Long-term average 30.5 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 29 hours spilling →	R.Thames ( Tidal )	4	29	down 90%	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief A EA ID / permit TWL00729 · 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 49 / 120 Long-term average 41.0 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 29 hours spilling →	Graveney	11	29	down 78%	100%
Chipping Warden WwTW Inlet overflow at sewage works Sewage works Chipping Warden Company site name Chipping Warden STW EA ID / permit TWL00095 · CTCR.1793 Outlet location SP5000048150 (OS grid reference) · View on Apple Maps WFD catchment Cherwell (Ashby Brook to Cropredy) (GB106039037350) 2024 spills / hours 61 / 361 Long-term average 39.9 spills a year (monitored since 2019) Monitor below 90% Comms failure / issue · Resolved - Aug Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 28 hours spilling →	Tributary of River Cherwell	11	28	down 82%	88%
Luton (East Hyde) WwTW Storm tank at sewage works Sewage works Luton Company site name East Hyde STW EA ID / permit TWL00284 · CNTD.0084 Outlet location TL1202018140 (OS grid reference) · View on Apple Maps WFD catchment Lee (from Luton Hoo Lakes to Hertford) (GB106038033392) 2024 spills / hours 20 / 73 Long-term average 7.6 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 28 hours spilling →	The River Lee	6	28	down 70%	98%
Leaden Roding WwTW Inlet overflow at sewage works Sewage works Leaden Roding Company site name Leaden Roding STW EA ID / permit TWL00261 · CSSC.1400 Outlet location TL5917013110 (OS grid reference) · View on Apple Maps WFD catchment Upper Roding (to Cripsey Brook) (GB106037033500) 2024 spills / hours 9 / 66 Long-term average 5.3 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 28 hours spilling →	Tributary of the River Roding	7	28	down 22%	100%
Greenwich PS CSO Storm discharge at pumping station Company site name Greenwich SPS & Storm SPS EA ID / permit TWL00203 · CSAB.0537 Outlet location TQ3819077940 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 12 / 92 Long-term average 10.2 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 26 hours spilling →	R.Thames ( Tidal )	4	26	down 67%	100%
Nightingale Lane CSO Overflow on sewer network Company site name Nightingale lane EA ID / permit TWL00311 · TEMP.2819 Outlet location TQ3417080200 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 44 / 53 Long-term average 21.9 spills a year (monitored since 2019) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 26 hours spilling →	River Thames	38	26	down 14%	100%
Cuddington WwTW Storm tank at sewage works (with treatment) Sewage works Cuddington Company site name Cuddington STW EA ID / permit TWL00146 · CSSC.2446 Outlet location SP7380011960 (OS grid reference) · View on Apple Maps WFD catchment Thame (Aylesbury to Scotsgrove Brook) (GB106039030370) Treatment Reed bed 2024 spills / hours 135 / 2,866 Long-term average 49.2 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 26 hours spilling →	River Thame	4	26	down 97%	100%
Streatham Storm Relief Overflow on sewer network Company site name Streatham storm relief B EA ID / permit TWL00730 · 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 / 2.3 Long-term average 17.8 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 26 hours spilling →	Graveney	18	26	up 1700%	100%
Brixton and Clapham Sr CSO Overflow on sewer network Company site name Brixton storm relief sewer EA ID / permit TWL00056 · CSAB.0554 Outlet location TQ3025078120 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 67 / 787 Long-term average 79.3 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 25 hours spilling →	R.Thames ( Tidal )	3	25	down 96%	100%
Darkes Lane, Potters Bar Overflow on sewer network Company site name Darkes lane, potters bar EA ID / permit TWL00545 · TEMP.2548 Outlet location TL2520001800 (OS grid reference) · View on Apple Maps WFD catchment Colne (upper east arm including Mimshall Brook) (GB106039029850) 2024 spills / hours 18 / 43 Long-term average 10.0 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 25 hours spilling →	Potters Bar Brook	9	25	down 50%	100%
Bentley Wastewater Treatment Works Inlet overflow at sewage works (with treatment) Sewage works Bentley Company site name Bentley STW EA ID / permit TWL00035 · CSSC.2455 Outlet location SU7900043670andSU7931043500 (OS grid reference) · View on Apple Maps WFD catchment North Wey (Alton to Tilford) and Alton Chalk (GB106039017830 and GB40601G604400) Treatment Reed bed 2024 spills / hours 62 / 707 Long-term average 79.1 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 24 hours spilling →	River Wey and Groundwater	4	24	down 94%	100%
Constable'S Piece WwTW Inlet overflow at sewage works (with treatment) Sewage works Constable S Piece Company site name Beckley STW EA ID / permit TWL00113 · CAWM.1403 Outlet location SP5668011940 (OS grid reference) · View on Apple Maps WFD catchment Oxon Ray (upstream A41 to Cherwell) including Otmoor (GB106039030090) Treatment Reed bed 2024 spills / hours 10 / 90 Long-term average 11.6 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 24 hours spilling →	Otmoor Lane Ditch	4	24	down 60%	100%
Western PS CSO Storm discharge at pumping station Company site name Western (Pimlico) SPS EA ID / permit TWL00440 · CSAB.0538 Outlet location TQ2868077920andTQ2864077910 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 18 / 74 Long-term average 16.8 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 24 hours spilling →	R.Thames ( Tidal )	5	24	down 72%	98%
Rowsham Wastewater Treatment Works Inlet overflow at sewage works Sewage works Rowsham Company site name Rowsham STW EA ID / permit TWL00355 · CSSC.1419 Outlet location SP8487017680 (OS grid reference) · View on Apple Maps WFD catchment Thame upstream of Aylesbury (GB106039030410) 2024 spills / hours 25 / 225 Long-term average 14.7 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 23 hours spilling →	Rowsham Brook	8	23	down 68%	100%
Millbank, Crawley Overflow on sewer network Company site name Millbank, crawley EA ID / permit TWL00302 · TEMP.2797 Outlet location TQ2451036480 (OS grid reference) · View on Apple Maps WFD catchment Ifield Brook (GB106039017460) 2024 spills / hours 3 / 21 Long-term average 2.0 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 23 hours spilling →	Mill Stream	5	23	up 67%	99%
Streatham & Balham Storm Relief B Overflow on sewer network Company site name Streatham & balham storm relief EA ID / permit TWL00394 · TEMP.2920 Outlet location TQ2712070900 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 5 / 3.8 Long-term average 25.0 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 21 hours spilling →	Graveney	18	21	up 260%	95%
Weston-on-the-green STW Pumping Sta Inlet overflow at sewage works Sewage works Weston On The Green Pumping Sta Company site name Weston-on-the-Green SPS EA ID / permit TWL00442 · TEMP.2220 Outlet location SP5370017400 (OS grid reference) · View on Apple Maps WFD catchment Gallos Brook (GB106039030130) 2024 spills / hours 3 / 34 Long-term average 9.5 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 21 hours spilling →	Gallos Brook	2	21	down 33%	100%
Wheathampstead Pumping Station Storm discharge at pumping station Company site name Wheathampstead SPS EA ID / permit TWL00763 · CSSC.7687 Outlet location TL1808014240 (OS grid reference) · View on Apple Maps WFD catchment Lee (from Luton Hoo Lakes to Hertford) (GB106038033392) 2024 spills / hours 12 / 87 Long-term average 7.5 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 21 hours spilling →	River Lee	3	21	down 75%	98%
Jews Row Pumping Station Storm discharge at pumping station Company site name Jews row pumping station (falconbrook storm relief) EA ID / permit TWL00424 · CSSA.0383 Outlet location TQ2592075420 (OS grid reference) · View on Apple Maps WFD catchment THAMES UPPER (GB530603911403) 2024 spills / hours 36 / 170 Long-term average 10.2 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 21 hours spilling →	Thames Tidal	4	21	down 89%	100%
Outside 135 Leeside Crescent Overflow on sewer network Company site name XX leeside crescent (formerly brookside road, golders green) EA ID / permit TWL00321 · CANM.0917 Outlet location TQ2427088380 (OS grid reference) · View on Apple Maps WFD catchment Dollis Brook and Upper Brent (GB106039022980) 2024 spills / hours 16 / 35 Long-term average 13.0 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 20 hours spilling →	The Decoy Brook	8	20	down 50%	100%
Tideway Combined Sewer Overflow Overflow on sewer network Company site name Tideway (beckton stw) EA ID / permit TWL00415 · EPRBP3220XF Outlet location TQ4548081510 (OS grid reference) · View on Apple Maps WFD catchment THAMES MIDDLE (GB530603911402) 2024 spills / hours 4 / 19 Long-term average 5.8 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 19 hours spilling →	River Thames (Tidal)	2	19	down 50%	100%
Hornton WwTW Storm tank at sewage works Sewage works Hornton Company site name Hornton STW EA ID / permit TWL00236 · CSSC.1383 Outlet location SP3969044760 (OS grid reference) · View on Apple Maps WFD catchment Sor Brook (Source to Broughton) (GB106039037320) 2024 spills / hours 47 / 504 Long-term average 17.3 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 19 hours spilling →	Hornton Stream	2	19	down 96%	100%
Opposite St Stephen's Hall Storm discharge at pumping station Company site name St Stephens Hall (Little London) SPS EA ID / permit TWL00319 · TEMP.1644 Outlet location SU6230059300 (OS grid reference) · View on Apple Maps WFD catchment Bow Brook (Pamber End to Bramley) (GB106039017160) 2024 spills / hours 72 / 181 Long-term average 40.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 18 hours spilling →	Bow Brook	21	18	down 71%	100%
Chigwell Road, Woodford Green Overflow on sewer network Company site name WINN VALLEY SPS LB REDBRIDGE 7 (CAVENDISH AVENUE) TQ40916107 CSO EA ID / permit TWL00788 · CETR.0232 Outlet location TQ4160091300 (OS grid reference) · View on Apple Maps WFD catchment Lower Roding (Loughton to Thames) (GB106037028181) 2024 spills / hours 34 / 30 Long-term average 28.7 spills a year (monitored since 2023) High-spill reason (company) Data collection - EDM non-representative location Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 18 hours spilling →	Roding	30	18	down 12%	100%
Waterloo Crescent Outfall Overflow on sewer network Company site name Waterloo crescent outfall, wokingham EA ID / permit TWL00756 · CSAC.0863 Outlet location SU8233067940 (OS grid reference) · View on Apple Maps WFD catchment Emm Brook (GB106039023130) 2024 spills / hours 29 / 267 Long-term average 18.0 spills a year (monitored since 2023) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 17 hours spilling →	Waterloo Road Stream	7	17	down 76%	100%
St Pauls Avenue CSO Overflow on sewer network EA ID / permit TWL00718 · Permit applied for Outlet location TQ1866788888 (OS grid reference) · View on Apple Maps WFD catchment Wealdstone Brook (GB106039022940) 2024 spills / hours 11 / 31 Long-term average 7.7 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 17 hours spilling →		4	17	down 64%	100%
Box Hill Storm discharge at pumping station Company site name Boxhill SPS EA ID / permit TWL00050 · TEMP.0505 Outlet location TQ1980052300 (OS grid reference) · View on Apple Maps WFD catchment Dorking North Downs Chalk (GB40601G602100) 2024 spills / hours 9 / 47 Long-term average 11.4 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 17 hours spilling →	Into Land	9	17	no change	95%
Codicote CSO Overflow on sewer network EA ID / permit TWL00811 · Unpermitted Outlet location TL2207118058 (OS grid reference) · View on Apple Maps WFD catchment Upper Lee Chalk (GB40601G602900) 2024 spills / hours – / – Monitor below 90% Capital / maintenance works affect EDM operation · Resolved - Mar Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 16 hours spilling →		12	16		78%

Sewage treatment works

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

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