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
Eversley (Lower Common) WwTW Storm tank at sewage works Sewage works Eversley Company site name New Mill STW EA ID / permit TWL00176 · CNTD.0078 Outlet location SU7600062880 (OS grid reference) · View on Apple Maps WFD catchment Blackwater (Hawley to Whitewater confluence at Bramshill) (GB106039017290) 2024 spills / hours 68 / 759 Long-term average 35.4 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 325 hours spilling →	Tributary of River Blackwater	27	325	down 60%	99%
Purton WwTW Storm tank at sewage works Sewage works Purton Company site name Purton STW EA ID / permit TWL00337 · CNTD.0051 Outlet location SU0890089240 (OS grid reference) · View on Apple Maps WFD catchment Key (Source to Thames) (GB106039023650) 2024 spills / hours 53 / 628 Long-term average 27.8 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 322 hours spilling →	Tributary of River Key	27	322	down 49%	100%
Shabbington WwTW Storm tank at sewage works (with treatment) Sewage works Shabbington Company site name Shabbington STW EA ID / permit TWL00363 · CSSC.1429 Outlet location SP6624007350 (OS grid reference) · View on Apple Maps WFD catchment Peppershill and Shabbington Brooks (GB106039030290) Treatment Reed bed 2024 spills / hours 67 / 999 Long-term average 37.0 spills a year (monitored since 2020) Monitor below 90% Installation set-up/design issue · Resolved - Nov Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 322 hours spilling →	Shabbington Brook	23	322	down 66%	88%
Banbury Wastewater Treatment Works Storm tank at sewage works Sewage works Banbury Company site name Banbury STW EA ID / permit TWL00025 · CNTD.0021 Outlet location SP4730040100 (OS grid reference) · View on Apple Maps WFD catchment Cherwell (Cropredy to Nell Bridge) (GB106039037310) 2024 spills / hours 126 / 1,861 Long-term average 52.3 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 314 hours spilling →	River Cherwell	26	314	down 79%	96%
Stansted Mountfitchet WwTW Storm tank at sewage works Sewage works Stansted Mountfitchet Company site name Stansted Mountfitchet STW EA ID / permit TWL00388 · CLCR.0165 Outlet location TL5009024270 (OS grid reference) · View on Apple Maps WFD catchment Stort and Bourne Brook (GB106038033340) 2024 spills / hours 64 / 923 Long-term average 29.3 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 313 hours spilling →	The River Stort	28	313	down 56%	99%
Grendon Underwood WwTW Storm tank at sewage works Sewage works Grendon Underwood Company site name Grendon Underwood STW EA ID / permit TWL00204 · TEMP.2626 Outlet location SP6799021150 (OS grid reference) · View on Apple Maps WFD catchment Ray and tributaries NorthEast of Grendon Underwood (GB106039030100) 2024 spills / hours 68 / 794 Long-term average 62.9 spills a year (monitored since 2018) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 306 hours spilling →	Oxon Ray	31	306	down 54%	100%
Haslemere WwTW Storm tank at sewage works (with treatment) Sewage works Haslemere Company site name Haslemere STW EA ID / permit TWL00217 · 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 52 / 573 Long-term average 52.5 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 303 hours spilling →	River Wey (South)	33	303	down 37%	100%
Heyford Wastewater Treatment Works Storm tank at sewage works Sewage works Heyford Company site name Upper Heyford STW EA ID / permit TWL00223 · TEMP.2658 Outlet location SP4928025430 (OS grid reference) · View on Apple Maps WFD catchment Cherwell (Nell Bridge to Bletchingdon) (GB106039037431) 2024 spills / hours 108 / 1,264 Long-term average 38.6 spills a year (monitored since 2018) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 303 hours spilling →	Cherwell	33	303	down 69%	95%
Bletchingdon WwTW Storm tank at sewage works Sewage works Bletchingdon Company site name Bletchingdon STW EA ID / permit TWL00043 · CTCR.1722 Outlet location SP5066017380 (OS grid reference) · View on Apple Maps WFD catchment Bletchingdon Stream (GB106039030080) 2024 spills / hours 120 / 1,871 Long-term average 75.1 spills a year (monitored since 2018) High-spill reason (company) Performance - Asset configuration (e.g. PS/rising main/storm tanks) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 302 hours spilling →	Bletchingdon Brook	32	302	down 73%	95%
Hartley Wintney WwTW Storm tank at sewage works Sewage works Hartley Wintney Company site name Hartley Wintney STW EA ID / permit TWL00216 · CNTD.0047 Outlet location SU7669058050 (OS grid reference) · View on Apple Maps WFD catchment Hart (Elvetham to Hartley Wintney) (GB106039017170) 2024 spills / hours 39 / 447 Long-term average 31.3 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 300 hours spilling →	Tributary of the River Hart	21	300	down 46%	100%
Dorking STW (Storm) Storm tank at sewage works Sewage works Dorking Company site name Dorking STW EA ID / permit TWL00159 · CASM.1027 Outlet location TQ1774050560 (OS grid reference) · View on Apple Maps WFD catchment Mole - Dorking to Leatherhead (GB106039017624) 2024 spills / hours 69 / 979 Long-term average 60.6 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 296 hours spilling →	River Mole	23	296	down 67%	99%
Chobham (Old) WwTW Storm tank at sewage works Sewage works Chobham Company site name Chobham STW EA ID / permit TWL00096 · TEMP.2484 Outlet location SU9770061000 (OS grid reference) · View on Apple Maps WFD catchment Addlestone Bourne (West End to Hale/Mill Bourne confluence at Mimbridge) (GB106039017920) 2024 spills / hours 78 / 884 Long-term average 60.7 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 288 hours spilling →	Bourne - South	20	288	down 74%	100%
Swindon WwTW Storm tank at sewage works (with treatment) Sewage works Swindon Company site name Swindon STW EA ID / permit TWL00402 · CNTD.0017 Outlet location SU1275086010 (OS grid reference) · View on Apple Maps WFD catchment Ray (Wiltshire) source to Lydiard Brook (GB106039023320) Treatment Reed bed 2024 spills / hours 47 / 622 Long-term average 38.4 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 288 hours spilling →	River Ray	23	288	down 51%	100%
Waddesdon WwTW Storm tank at sewage works Sewage works Waddesdon Company site name Waddesdon STW EA ID / permit TWL00420 · CNTD.0052 Outlet location SP7488017950 (OS grid reference) · View on Apple Maps WFD catchment Fleet Marston Brook, Denham Brook, Pitchcott Brook west (GB106039030420) 2024 spills / hours 63 / 967 Long-term average 62.3 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 281 hours spilling →	Fleet Marston Brook	25	281	down 60%	100%
Chipping Norton WwTW Storm tank at sewage works (with treatment) Sewage works Chipping Norton Company site name Chipping Norton STW EA ID / permit TWL00094 · CTCR.1767 Outlet location SP2939026650 (OS grid reference) · View on Apple Maps WFD catchment Cornwell Brook and tributaries (Source to Evenlode) (GB106039037400) Treatment Reed bed 2024 spills / hours 56 / 835 Long-term average 24.8 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 277 hours spilling →	Blue Brook	21	277	down 63%	100%
Pangbourne WwTW Inlet overflow at sewage works (with treatment) Sewage works Pangbourne Company site name Pangbourne STW EA ID / permit TWL00324 · CTCA.2077 Outlet location SU6440076600 (OS grid reference) · View on Apple Maps WFD catchment Sulham Brook (GB106039023280) Treatment Reed bed 2024 spills / hours 70 / 1,291 Long-term average 15.7 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 271 hours spilling →	River Sul	14	271	down 80%	100%
Farnham Storm tank at sewage works Sewage works Farnham Company site name Farnham STW EA ID / permit TWL00182 · TEMP.2589 Outlet location SU8530047400 (OS grid reference) · View on Apple Maps WFD catchment North Wey (Alton to Tilford) (GB106039017830) 2024 spills / hours 52 / 530 Long-term average 35.9 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 269 hours spilling →	Farnham Park Tributary	27	269	down 48%	100%
Cobham Bridge, Adj Cobham Ps Overflow on sewer network Company site name Cobham EA ID / permit TWL00107 · TEMP.2528 Outlet location TQ0993060740 (OS grid reference) · View on Apple Maps WFD catchment Mole - Leatherhead to Hersham (GB106039017623) 2024 spills / hours 53 / 644 Long-term average 30.9 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 268 hours spilling →	Mole	24	268	down 55%	100%
Great Bedwyn WwTW Storm tank at sewage works Sewage works Great Bedwyn Company site name Great Bedwyn STW EA ID / permit TWL00201 · CSSC.2350 Outlet location SU2836064900 (OS grid reference) · View on Apple Maps WFD catchment Kennet and Avon Canal, summit to Copse Lock (GB70610181) 2024 spills / hours 67 / 1,107 Long-term average 25.9 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 267 hours spilling →	Kennet and Avon Canal	18	267	down 73%	100%
Worminghall STW Inlet overflow at sewage works Sewage works Worminghall Company site name Worminghall STW EA ID / permit TWL00464 · CTCR.1975 Outlet location SP6500009100 (OS grid reference) · View on Apple Maps WFD catchment Worminghall Brook and tributaries (GB106039030340) 2024 spills / hours 93 / 1,215 Long-term average 42.4 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 264 hours spilling →	Worminghallbrook	23	264	down 75%	100%
Wingrave Wastewater Treatment Works Storm tank at sewage works Sewage works Wingrave Company site name Wingrave STW EA ID / permit TWL00453 · CSSC.2320 Outlet location SP8649018720 (OS grid reference) · View on Apple Maps WFD catchment Thame upstream of Aylesbury (GB106039030410) 2024 spills / hours 88 / 1,334 Long-term average 82.9 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 257 hours spilling →	Tributary of Rowsham Brook	29	257	down 67%	99%
Shutford Wastewater Treatment Works Inlet overflow at sewage works Sewage works Shutford Company site name Shutford STW EA ID / permit TWL00369 · CSSC.1434 Outlet location SP3883040790 (OS grid reference) · View on Apple Maps WFD catchment Shutford Stream (Source to Sor Brook) (GB106039037300) 2024 spills / hours 190 / 2,977 Long-term average 74.7 spills a year (monitored since 2019) High-spill reason (company) Performance - Asset configuration (e.g. PS/rising main/storm tanks) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 255 hours spilling →	Shutford Stream	32	255	down 83%	95%
Chapel Row (Berks) WwTW Storm tank at sewage works Sewage works Chapel Row Company site name Chapel Row STW EA ID / permit TWL00081 · CSSC.2466 Outlet location SU5745069340 (OS grid reference) · View on Apple Maps WFD catchment Pang (GB106039023300) 2024 spills / hours 112 / 1,979 Long-term average 66.4 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 253 hours spilling →	Tributary of River Bourne	21	253	down 81%	95%
Arborfield WwTW Storm tank at sewage works Sewage works Arborfield Company site name Arborfield STW EA ID / permit TWL00014 · CNTD.0020 Outlet location SU7678067380 (OS grid reference) · View on Apple Maps WFD catchment Barkham Brook (GB106039017400) 2024 spills / hours 53 / 522 Long-term average 27.5 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 251 hours spilling →	Barkham Brook	28	251	down 47%	100%
Aldermaston WwTW Inlet overflow at sewage works (with treatment) Sewage works Aldermaston Company site name Aldermaston STW EA ID / permit TWL00006 · TEMP.2345 Outlet location SU5912065510 (OS grid reference) · View on Apple Maps WFD catchment Aldermaston Bagshot Beds (GB40602G601500) Treatment Reed bed 2024 spills / hours 48 / 418 Long-term average 61.6 spills a year (monitored since 2019) High-spill reason (company) Performance - Asset configuration (e.g. PS/rising main/storm tanks) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 248 hours spilling →	Groundwater via Land Treatment	31	248	down 35%	100%
Slough Wastewater Treatment Works Storm tank at sewage works (with treatment) Sewage works Slough Company site name Slough STW EA ID / permit TWL00397 · CNTM.2237 Outlet location SU9376079420 (OS grid reference) · View on Apple Maps WFD catchment Roundmoor Ditch and Boveney Ditch (GB106039023540) Treatment Reed bed 2024 spills / hours 70 / 1,221 Long-term average 24.5 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 246 hours spilling →	Roundmoor Ditch	14	246	down 80%	99%
Thornwood WwTW Storm tank at sewage works Sewage works Thornwood Company site name Thornwood STW EA ID / permit TWL00414 · CSSC.1445 Outlet location TL4765005030 (OS grid reference) · View on Apple Maps WFD catchment Cripsey Brook (GB106037033481) 2024 spills / hours 71 / 738 Long-term average 45.9 spills a year (monitored since 2018) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 241 hours spilling →	The Cripsey Brook	31	241	down 56%	100%
Esher Wastewater Treatment Works Storm tank at sewage works Sewage works Esher Company site name Esher STW EA ID / permit TWL00174 · CNTD.0044 Outlet location TQ1303065980 (OS grid reference) · View on Apple Maps WFD catchment Mole (Hersham to R. Thames conf at East Molesey) (GB106039017622) 2024 spills / hours 78 / 1,262 Long-term average 50.4 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 239 hours spilling →	River Ember and Mole	19	239	down 76%	100%
Codicote CSO (Rabley Heath Road, Codicote) (Gwa site) Overflow on sewer network EA ID / permit TWL00108 · Unpermitted Outlet location TL2207118058 (OS grid reference) · View on Apple Maps WFD catchment Upper Lee Chalk (GB40601G602900) 2024 spills / hours 25 / 86 Long-term average 34.6 spills a year (monitored since 2019) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 225 hours spilling →		31	225	up 24%	100%
Bucklebury Storm tank at sewage works Sewage works Bucklebury Company site name Briff Lane (Bucklebury) STW EA ID / permit TWL00061 · TEMP.2421 Outlet location SU5470069801 (OS grid reference) · View on Apple Maps WFD catchment Pang (GB106039023300) 2024 spills / hours 73 / 834 Long-term average 53.5 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 221 hours spilling →	Briff Lane Stream	23	221	down 68%	100%
Coach Road CSO on Stonebridge Sewer Overflow on sewer network Company site name Stonebridge sso, brockham EA ID / permit TWL00106 · CSAC.0953 Outlet location TQ1928049560 (OS grid reference) · View on Apple Maps WFD catchment Mole - Horley to Dorking (GB106039017625) 2024 spills / hours 11 / 122 Long-term average 19.3 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 218 hours spilling →	The River Mole	26	218	up 136%	98%
Bracknell WwTW Storm tank at sewage works Sewage works Bracknell Company site name Bracknell STW EA ID / permit TWL00051 · CTCR.1973 Outlet location SU8537072050 (OS grid reference) · View on Apple Maps WFD catchment Cut (Binfield to River Thames confluence) and Maidenhead Ditch (GB106039023510) 2024 spills / hours 53 / 615 Long-term average 53.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 215 hours spilling →	The Cut	19	215	down 64%	99%
Berkhamsted Sewage Treatment Works Storm tank at sewage works Sewage works Berkhamsted Company site name Berkhamsted STW EA ID / permit TWL00037 · CATM.3074 Outlet location TL0131006810 (OS grid reference) · View on Apple Maps WFD catchment Grand Union Canal, Berkhamstead to Maple Lodge (RIvers Bulbourne, Gade and Colne) (GB70610185) 2024 spills / hours 157 / 1,776 Long-term average 92.6 spills a year (monitored since 2019) High-spill reason (company) Performance - Asset configuration (e.g. PS/rising main/storm tanks) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 210 hours spilling →	The Grand Union Canal	35	210	down 78%	100%
Little Hallingbury WwTW Storm tank at sewage works Sewage works Little Hallingbury Company site name Little Hallingbury STW EA ID / permit TWL00269 · CSSC.0263 Outlet location TL4944017430 (OS grid reference) · View on Apple Maps WFD catchment Little Hallingbury Brook (GB106038033250) 2024 spills / hours 50 / 711 Long-term average 36.0 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 209 hours spilling →	Little Hallingbury Brook	26	209	down 48%	100%
Marsh Gibbon Storm tank at sewage works Sewage works Marsh Gibbon Company site name Marsh Gibbon STW EA ID / permit TWL00294 · TEMP.2765 Outlet location SP6440022501 (OS grid reference) · View on Apple Maps WFD catchment Summerstown Ditch and Launton and Cutters Brook (GB106039030120) 2024 spills / hours 69 / 845 Long-term average 72.0 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 208 hours spilling →	Summerstown Ditch	22	208	down 68%	99%
Merstham WwTW Storm tank at sewage works Sewage works Merstham Company site name Merstham STW EA ID / permit TWL00297 · CNTM.0081 Outlet location TQ2968052120 (OS grid reference) · View on Apple Maps WFD catchment Redhill Brook (GB106039017590) 2024 spills / hours 26 / 320 Long-term average 24.1 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 206 hours spilling →	Redhill Brook	19	206	down 27%	100%
Mogden WwTW Storm tank at sewage works Sewage works Mogden Company site name Mogden STW EA ID / permit TWL00304 · CNTD.0085 Outlet location TQ1675075500 (OS grid reference) · View on Apple Maps WFD catchment THAMES UPPER (GB530603911403) 2024 spills / hours 50 / 472 Long-term average 32.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 203 hours spilling →	River Thames Tidal	17	203	down 66%	100%
Brentwood (Nags Head Lane) WwTW Storm tank at sewage works Sewage works Brentwood Company site name Nags Head Lane STW EA ID / permit TWL00054 · CSSC.0328 Outlet location TQ5624091580 (OS grid reference) · View on Apple Maps WFD catchment Ingrebourne (GB106037028130) 2024 spills / hours 46 / 491 Long-term average 43.9 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 192 hours spilling →	River Ingrebourne	17	192	down 63%	97%
Clanfield WwTW Storm tank at sewage works Sewage works Clanfield Company site name Clanfield STW EA ID / permit TWL00103 · CSSC.1001 Outlet location SP2900001810 (OS grid reference) · View on Apple Maps WFD catchment Radcot Cut (GB106039030231) 2024 spills / hours 172 / 3,403 Long-term average 111.9 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 185 hours spilling →	Halfacre Brook	14	185	down 92%	97%
Blind Mans Gate, Highclere Storm discharge at pumping station Company site name Blind Mans Gate (Highclere) SPS EA ID / permit TWL00044 · TEMP.0482 Outlet location SU4380061800 (OS grid reference) · View on Apple Maps WFD catchment Penwood Stream (GB106039017210) 2024 spills / hours 45 / 473 Long-term average 29.6 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 183 hours spilling →	Penwood Stream	21	183	down 53%	100%
Ray Lodge Road Overflow on sewer network Company site name Ray lodge road XX EA ID / permit TWL00695 · CANM.0717 Outlet location TQ4186091810 (OS grid reference) · View on Apple Maps WFD catchment Lower Roding (Loughton to Thames) (GB106037028181) 2024 spills / hours 73 / 364 Long-term average 67.1 spills a year (monitored since 2018) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 183 hours spilling →	To River Roding	56	183	down 23%	100%
Littlemead Industrial Estate CSO Overflow on sewer network Company site name Littlemead ind estate, cranleigh EA ID / permit TWL00272 · CTCR.1941 Outlet location TQ0484038990 (OS grid reference) · View on Apple Maps WFD catchment Cranleigh Waters (GB106039017810) 2024 spills / hours 52 / 414 Long-term average 38.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 183 hours spilling →	Trib of Cranleigh Waters	16	183	down 69%	98%
Pirbright (Hockford) WwTW Storm tank at sewage works Sewage works Pirbright Company site name Hockford STW EA ID / permit TWL00331 · CNTD.0037 Outlet location SU9589054170 (OS grid reference) · View on Apple Maps WFD catchment Hoe Stream (Pirbright to River Wey confluence at Woking) (GB106039017900) 2024 spills / hours 73 / 537 Long-term average 37.0 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 175 hours spilling →	Stanford Brook	24	175	down 67%	100%
Wantage (storm) Storm tank at sewage works Sewage works Wantage Company site name Wantage STW EA ID / permit TWL00425 · TEMP.2989 Outlet location SU4070091701 (OS grid reference) · View on Apple Maps WFD catchment Letcombe Brook (GB106039023350) 2024 spills / hours 96 / 650 Long-term average 37.5 spills a year (monitored since 2018) High-spill reason (company) Performance - SW Infiltration Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 170 hours spilling →	Letcombe Brook	30	170	down 69%	100%
Reading Sewage Treatment Works Storm tank at sewage works Sewage works Reading Company site name Reading STW EA ID / permit TWL00343 · CAWM.0942 Outlet location SU7113070720 (OS grid reference) · View on Apple Maps WFD catchment Foudry Brook (West End Brook to M4) (GB106039017380) 2024 spills / hours 47 / 654 Long-term average 16.7 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 169 hours spilling →	Foudry Brook	14	169	down 70%	99%
Amersham Balancing Tanks Overflow on sewer network Company site name Amersham balancing tanks/amersham vale stk EA ID / permit TWL00009 · TEMP.2368 Outlet location SU9790096100 (OS grid reference) · View on Apple Maps WFD catchment Misbourne (GB106039029830) 2024 spills / hours 210 / 4,843 Long-term average 74.7 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 167 hours spilling →	Misbourne	13	167	down 94%	100%
Charlwood PS Overflow on sewer network Company site name Charlwood, surrey EA ID / permit TWL00086 · CTCR.1926 Outlet location TQ2497040960 (OS grid reference) · View on Apple Maps WFD catchment Mole upstream of Horley (GB106039017481) 2024 spills / hours 35 / 268 Long-term average 21.9 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 167 hours spilling →	Mans Brook	25	167	down 29%	92%
Horley (Oxon) WwTW Inlet overflow at sewage works Sewage works Horley Company site name Horley (Oxon) STW EA ID / permit TWL00235 · TEMP.2667 Outlet location SP4223043380 (OS grid reference) · View on Apple Maps WFD catchment Sor Brook (Source to Broughton) (GB106039037320) 2024 spills / hours 120 / 1,382 Long-term average 48.3 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 162 hours spilling →	Sor Brook	23	162	down 81%	100%
Lechlade WwTW Storm tank at sewage works Sewage works Lechlade Company site name Lechlade STW EA ID / permit TWL00263 · CTCR.1797 Outlet location SU2271099330 (OS grid reference) · View on Apple Maps WFD catchment Leach (Source to Thames) (GB106039030040) 2024 spills / hours 128 / 2,366 Long-term average 35.8 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 161 hours spilling →	River Leach	11	161	down 91%	100%
Easthampstead Park Storm tank at sewage works Sewage works Easthampstead Park Company site name Easthampstead Park STW EA ID / permit TWL00169 · TEMP.2561 Outlet location SU8390066401 (OS grid reference) · View on Apple Maps WFD catchment Emm Brook (GB106039023130) 2024 spills / hours 42 / 331 Long-term average 20.3 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 160 hours spilling →	Emm Brook	16	160	down 62%	98%

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.