Overflow history upstream of River Avon, Warleigh Weir, Bath
The spot's forecast · For event organisers
This page lists the monitored storm overflows upstream of this spot and how often each spilled in each year. It is not a water test, and it does not say whether the water is fit to swim in. It does not include farm runoff, misconnected drains, treated sewage effluent, wildlife or overflows without a monitor. A year's count depends on how long the monitor worked, shown as monitor uptime.
Each year, all overflows upstream
| Year | Overflows with a return | Spills | Spill hours | Spill hours, weighted by reach |
|---|---|---|---|---|
| 2021 | 93 | 2,168 | 10,832 | 278 |
| 2022 | 122 | 2,714 | 15,354 | 640 |
| 2023 | 162 | 5,776 | 48,193 | 2,356 |
| 2024 | 162 | 6,160 | 53,071 | 3,020 |
| 2025 | 165 | 3,264 | 22,796 | 999 |
Reach is the share of a spill's bacteria SwimSignal's model expects to arrive here, after die-off on the way and dilution by the river. Weighting by it counts an hour of spilling just upstream for far more than one 40 km away. Spills are counted by the Environment Agency's 12/24 method: any discharge in the first 12 hours counts as one spill, then one more for each 24 hours with any discharge. How reach is worked out.
The overflows, by reach
All 185, the one whose spills matter most here first. Hours away is how long sewage takes to arrive at the model's river speed.
| Overflow and id | Company | km upstream | Hours away | Reach | Spills 2023 | Spills 2024 | Spills 2025 | Spill hours 2025 | Monitor uptime 2025 |
|---|---|---|---|---|---|---|---|---|---|
| Freshford storm tank overflow Freshford Storm Tank · WXW00449 | Wessex Water | 4.5 | 2 | 69% | 57 | 81 | 32 | 361 | 100% |
| Winsley storm tank overflow Winsley Storm Tank · WXW01270 | Wessex Water | 5.4 | 3 | 66% | 22 | 21 | 6 | 20 | 100% |
| Bradford-on-Avon pumping station overflow Bradford-ON-Avon Inlet PS Inlet · WXW00162 | Wessex Water | 7.8 | 4 | 37% | 0 | 0 | – | – | 100% |
| Saint Aldhelms Barton Bridge Barton Farm (175M DS) WXW00105 | Wessex Water | 8.4 | 5 | 36% | 8 | 16 | 8 | 53 | 96% |
| Bradford-ON-Avon Culver Street Recreation Park WXW00884 | Wessex Water | 8.5 | 5 | 35% | 58 | 54 | 4 | 11 | 100% |
| Bradford-ON-Avon Market Street Junction With Church Street WXW00686 | Wessex Water | 9.1 | 5 | 35% | 56 | 64 | 47 | 53 | 100% |
| Bradford-ON-Avon Market Street/ Silver Street Junction WXW00996 | Wessex Water | 9.1 | 5 | 35% | 19 | 24 | 8 | 48 | 85% |
| WSX10094 WSX10094 | Wessex Water | 9.4 | 5 | 34% | – | – | – | – | – |
| Bradford-ON-Avon Spring Field AND Woolley Street Junction WXW01283 | Wessex Water | 9.4 | 5 | 34% | 28 | 38 | 18 | 50 | 95% |
| WSX10043 WSX10043 | Wessex Water | 9.7 | 5 | 34% | – | – | – | – | – |
| WSX10008 WSX10008 | Wessex Water | 10.3 | 6 | 33% | – | – | – | – | – |
| Freshford NEW INN WXW00788 | Wessex Water | 5.8 | 3 | 24% | 9 | 16 | 4 | 14 | 100% |
| Freshford Fields OFF Rosemary Lane WXW00979 | Wessex Water | 6.6 | 4 | 24% | 63 | 67 | 29 | 63 | 99% |
| Westwood storm tank overflow Westwood Storm Tank · WXW01243 | Wessex Water | 8.6 | 5 | 22% | 33 | 62 | 30 | 421 | 99% |
| WSX10004 WSX10004 | Wessex Water | 19.1 | 11 | 17% | – | – | – | – | – |
| Melksham Semington Road O/S Police Station WXW00971 | Wessex Water | 20.5 | 11 | 16% | 33 | 41 | 22 | 81 | 100% |
| Melksham Semington Roundabout WXW00973 | Wessex Water | 20.5 | 11 | 16% | 0 | 11 | 2 | 13 | 100% |
| Melksham storm tank overflow Melksham Storm Tank · WXW00708 | Wessex Water | 21.0 | 12 | 16% | 45 | 52 | 20 | 308 | 100% |
| Rode storm tank overflow Rode Storm Tank · WXW00936 | Wessex Water | 15.2 | 8 | 15% | 102 | 82 | 39 | 522 | 100% |
| Melksham Inlet WXW00707 | Wessex Water | 21.3 | 12 | 15% | 70 | 83 | 51 | 496 | 100% |
| Rode Barrow Farm Tank WXW00935 | Wessex Water | 15.6 | 9 | 15% | 4 | 5 | 3 | 7 | 97% |
| Monkton Combe Mill Lane WXW00729 | Wessex Water | 4.0 | 2 | 14% | 60 | 61 | 49 | 46 | 95% |
| WSX10090 WSX10090 | Wessex Water | 4.0 | 2 | 14% | – | – | – | – | – |
| Midford Tucking Mill WXW00720 | Wessex Water | 5.2 | 3 | 13% | 30 | 43 | 18 | 78 | 100% |
| Beckington storm tank overflow Beckington Storm Tank · WXW00120 | Wessex Water | 18.9 | 10 | 12% | 31 | 55 | 11 | 132 | 100% |
| Midford ADJ Abandoned Railway WXW00719 | Wessex Water | 5.7 | 3 | 12% | 3 | 4 | 2 | 0 | 100% |
| Melksham Semington Road WXW00972 | Wessex Water | 19.4 | 11 | 12% | 18 | 16 | 6 | 49 | 100% |
| Bowerhill Shails Lane storm tank overflow Bowerhill Shails Lane Storm Tank · WXW00160 | Wessex Water | 19.4 | 11 | 12% | 60 | 66 | 33 | 373 | 100% |
| Bowerhill Shails Lane Inlet WXW00159 | Wessex Water | 19.4 | 11 | 12% | 24 | 29 | 12 | 40 | 100% |
| Thingley Coppershell Lane storm tank overflow Thingley Coppershell Lane Storm Tank · WXW01133 | Wessex Water | 26.7 | 15 | 11% | 65 | 69 | 38 | 509 | 100% |
| Lacock storm tank overflow Lacock Storm Tank · WXW00606 | Wessex Water | 26.8 | 15 | 11% | 92 | 75 | 8 | 49 | 100% |
| Thingley Coppershell Lane Inlet WXW01132 | Wessex Water | 26.7 | 15 | 11% | 7 | 8 | 2 | 3 | 100% |
| Chippenham Blackwell Hams storm tank overflow Chippenham Blackwell Hams Storm Tank · WXW00278 | Wessex Water | 34.8 | 19 | 7% | 84 | 88 | 39 | 492 | 100% |
| Chippenham Blackwell Hams Inlet WXW00277 | Wessex Water | 34.8 | 19 | 7% | 0 | 3 | 1 | 4 | 100% |
| Chippenham Westmead WXW01237 | Wessex Water | 35.8 | 20 | 6% | 21 | 24 | 6 | 67 | 100% |
| WSX10046 WSX10046 | Wessex Water | 36.6 | 20 | 6% | – | – | – | – | – |
| Chippenham Wood Lane WXW01275 | Wessex Water | 36.3 | 20 | 6% | 7 | 10 | 7 | 2 | 100% |
| Chippenham THE IVY WXW00258 | Wessex Water | 36.7 | 20 | 6% | 1 | 2 | 1 | 4 | 95% |
| Chippenham, High Street O/S 6 storm overflow Chippenham - High Street O/S 6 - Combined Sewer Overflow · WXW00355 | Wessex Water | 37.1 | 21 | 6% | 69 | 63 | 47 | 93 | 100% |
| Chippenham Monkton Park Offices WXW00749 | Wessex Water | 37.3 | 21 | 6% | 16 | 19 | 6 | 21 | 100% |
| Chippenham, High Street OPP 25 storm overflow Chippenham - High Street OPP 25 - Combined Sewer Overflow · WXW01326 | Wessex Water | 37.1 | 21 | 6% | – | – | 1 | 0 | 100% |
| Chippenham Commons Slip WXW00698 | Wessex Water | 37.9 | 21 | 5% | 0 | 2 | 1 | 0 | 100% |
| WSX0572 WSX0572 | Wessex Water | 38.3 | 21 | 5% | – | – | – | – | – |
| Chippenham 16 Long Close WXW00637 | Wessex Water | 38.3 | 21 | 5% | 42 | 44 | 6 | 5 | 100% |
| Chippenham, Long Close pumping station storm tank overflow Chippenham - Long Close - Sewage Pumping Station - Storm Tank · WXW01327 | Wessex Water | 38.3 | 21 | 5% | – | – | 2 | 7 | 100% |
| Chippenham, 22 Long Close storm overflow Chippenham - 22 Long Close - Combined Sewer Overflow · WXW01298 | Wessex Water | 38.4 | 21 | 5% | – | – | 0 | 0 | 100% |
| Trowbridge Canal Road WXW00607 | Wessex Water | 13.4 | 7 | 5% | 32 | 41 | 21 | 165 | 100% |
| Frome Welshmill Lane storm tank overflow Frome Welshmill Lane Storm Tanks Storm Tank · WXW00454 | Wessex Water | 24.6 | 14 | 5% | 33 | 43 | 22 | 60 | 100% |
| Frome Whatcombe Road NO 20 WXW01245 | Wessex Water | 24.5 | 14 | 5% | 42 | 45 | 31 | 10 | 100% |
| Frome Farrant Road Near Youth Centre WXW01297 | Wessex Water | 24.3 | 14 | 5% | 47 | 40 | 21 | 7 | 97% |
| Trowbridge Bradford Road Inlet WXW01155 | Wessex Water | 14.2 | 8 | 5% | 17 | 31 | 11 | 112 | 100% |
| Frome Welshmill Lane Inlet 2 WXW01335 | Wessex Water | 24.6 | 14 | 5% | – | – | 0 | 0 | 100% |
| Frome Welshmill Lane Inlet WXW00453 | Wessex Water | 24.6 | 14 | 5% | 20 | 2 | 0 | 0 | 100% |
| Trowbridge, Bowyers Factory Culvert storm overflow Trowbridge - Bowyers Factory Culvert - Combined Sewer Overflow · WXW01364 | Wessex Water | 14.6 | 8 | 5% | – | – | – | – | – |
| Trowbridge Stallard Street O/S 58 WXW01047 | Wessex Water | 14.6 | 8 | 5% | 1 | 4 | 2 | 1 | 97% |
| Trowbridge THE Shires Multi-Storey CAR Park/Basement WXW00990 | Wessex Water | 14.6 | 8 | 5% | 0 | 0 | 0 | 0 | 100% |
| Trowbridge, Town Bridge storm overflow Trowbridge - Town Bridge - Combined Sewer Overflow · WXW01352 | Wessex Water | 14.6 | 8 | 5% | – | – | 0 | 0 | 100% |
| Frome Court House King Street WXW00333 | Wessex Water | 25.6 | 14 | 4% | 29 | 35 | 19 | 6 | 100% |
| Frome Merchants Barton WXW00711 | Wessex Water | 25.6 | 14 | 4% | 24 | 35 | 17 | 4 | 100% |
| Frome Westway Precinct CAR Park R/O WXW01242 | Wessex Water | 25.4 | 14 | 4% | 5 | 2 | 3 | 0 | 100% |
| Frome Singers Cattle Market WXW00051 | Wessex Water | 25.5 | 14 | 4% | 16 | 9 | 6 | 1 | 100% |
| Wellow Inlet WXW01206 | Wessex Water | 10.8 | 6 | 4% | 45 | 55 | 2 | 5 | 100% |
| Frome Rodden Road WXW00934 | Wessex Water | 26.1 | 14 | 4% | 6 | 5 | 2 | 2 | 100% |
| Wellow Mill Hill WXW00727 | Wessex Water | 11.3 | 6 | 4% | 0 | 2 | 0 | 0 | 100% |
| Frome North OF Carpet Factory Near Railway Junction WXW00805 | Wessex Water | 26.6 | 15 | 4% | 7 | 5 | 4 | 1 | 100% |
| Frome Wallbridge WXW01185 | Wessex Water | 26.8 | 15 | 4% | 4 | 6 | 3 | 11 | 100% |
| Frome Portway / Locks Hill WXW00880 | Wessex Water | 26.8 | 15 | 4% | 15 | 19 | 17 | 2 | 100% |
| Trowbridge Wicker Hill O/S Mane Event Hairdressers WXW00046 | Wessex Water | 15.6 | 9 | 4% | 1 | 1 | 0 | 0 | 100% |
| Shoscombe Single Hill WXW00997 | Wessex Water | 15.2 | 8 | 3% | 0 | 2 | 0 | 0 | 100% |
| Shoscombe storm tank overflow Shoscombe Storm Tank · WXW00992 | Wessex Water | 15.9 | 9 | 3% | 69 | 101 | 41 | 342 | 100% |
| WSX10119 WSX10119 | Wessex Water | 40.5 | 22 | 3% | – | – | – | – | – |
| Frome Adderwell Close WXW00062 | Wessex Water | 27.7 | 15 | 3% | 69 | 72 | 58 | 107 | 100% |
| Frome Lower Keyford WXW00654 | Wessex Water | 27.8 | 16 | 3% | 74 | 69 | 58 | 81 | 100% |
| Frome Feltham Drive Near Footbridge WXW00420 | Wessex Water | 27.8 | 16 | 3% | 16 | 5 | 13 | 1 | 100% |
| Dunkerton Brooklands WXW00203 | Wessex Water | 13.0 | 7 | 3% | 7 | 31 | 7 | 44 | 100% |
| CAM Valley Dunkerton Inlet WXW00225 | Wessex Water | 14.2 | 8 | 3% | 67 | 82 | 28 | 29 | 100% |
| CAM Valley Splot Farm NR Peasedown ST John WXW01029 | Wessex Water | 14.6 | 8 | 3% | 0 | 7 | 2 | 3 | 100% |
| Radstock Mill Lane storm tank overflow Radstock Mill Lane Storm Tank · WXW00913 | Wessex Water | 18.5 | 10 | 3% | 118 | 85 | 49 | 407 | 100% |
| Carlingcott Stoneage Lane WXW01073 | Wessex Water | 15.1 | 8 | 3% | 31 | 39 | 28 | 156 | 100% |
| WSX10063 WSX10063 | Wessex Water | 19.0 | 11 | 2% | – | – | – | – | – |
| Radstock Mill Lane Inlet 1 WXW00911 | Wessex Water | 18.6 | 10 | 2% | 12 | 6 | 13 | 38 | 100% |
| Radstock Mill Lane Inlet 2 WXW00912 | Wessex Water | 18.6 | 10 | 2% | 12 | 11 | 14 | 45 | 100% |
| Radstock Waterloo Road/Pine Court WXW00860 | Wessex Water | 19.0 | 11 | 2% | 26 | 23 | 10 | 16 | 83% |
| Radstock Walegrave Terrace OPP 9 WXW01184 | Wessex Water | 19.0 | 11 | 2% | 0 | 0 | 0 | 0 | 100% |
| Radstock Waterloo Road (Downstream) storm overflow Radstock Waterloo Road SO (Downstream) · WXW01162 | Wessex Water | 19.0 | 11 | 2% | 2 | 3 | 0 | 0 | 95% |
| Radstock Frome Road WXW00452 | Wessex Water | 19.3 | 11 | 2% | 1 | 6 | 1 | 0 | 100% |
| Peasedown ST John NEW Buildings / Whitebrook Lane WXW00785 | Wessex Water | 15.5 | 9 | 2% | 26 | 47 | 27 | 6 | 100% |
| Camerton Bridge Place Road MH D19 WXW00174 | Wessex Water | 16.9 | 9 | 2% | 7 | 16 | 5 | 8 | 100% |
| Camerton Sunnyvale WXW01089 | Wessex Water | 17.1 | 10 | 2% | 0 | 1 | 0 | 0 | 100% |
| Sutton Benger Inlet WXW01090 | Wessex Water | 46.8 | 26 | 2% | 92 | 134 | 62 | 972 | 100% |
| Timsbury Radford Hill WXW00909 | Wessex Water | 18.5 | 10 | 2% | 52 | 51 | 30 | 76 | 100% |
| Christian Malford Church Road WXW00287 | Wessex Water | 46.7 | 26 | 2% | 1 | 0 | 0 | 0 | 99% |
| Paulton storm tank overflow Paulton Storm Tank · WXW00848 | Wessex Water | 20.2 | 11 | 2% | 101 | 99 | 57 | 844 | 100% |
| Paulton Goosard Bridge WXW00473 | Wessex Water | 20.5 | 11 | 2% | 62 | 63 | 47 | 206 | 100% |
| North Bradley Churchlands WXW00814 | Wessex Water | 21.5 | 12 | 2% | 0 | 1 | 0 | 0 | 100% |
| Paulton Works OFF Bristol Road WXW00186 | Wessex Water | 21.0 | 12 | 2% | 41 | 38 | 21 | 60 | 100% |
| Hallatrow WXW00492 | Wessex Water | 22.4 | 12 | 1% | 20 | 24 | 7 | 13 | 100% |
| Mells WXW00709 | Wessex Water | 29.4 | 16 | 1% | 3 | 4 | 0 | 0 | 100% |
| Radstock Waterloo Road Builders Yard WXW00930 | Wessex Water | 19.5 | 11 | 1% | 1 | 0 | 0 | 0 | 94% |
| Broughton Gifford THE Green WXW01121 | Wessex Water | 20.0 | 11 | 1% | 25 | 31 | 14 | 170 | 100% |
| Radstock Somervale Road Rear Khandalla Welton Road WXW01008 | Wessex Water | 20.4 | 11 | 1% | 51 | 53 | 40 | 25 | 100% |
| Broughton Gifford Curtis Orchard WXW00359 | Wessex Water | 20.1 | 11 | 1% | 11 | 14 | 7 | 77 | 100% |
| Midsomer Norton Storm Retention Tank (OLD STW) WXW01212 | Wessex Water | 20.9 | 12 | 1% | 49 | 57 | 28 | 92 | 100% |
| Monkton Combe Summer Lane WXW01085 | Wessex Water | 5.0 | 3 | 1% | 31 | 37 | 27 | 13 | 100% |
| Temple Cloud Bridge WXW01107 | Wessex Water | 24.3 | 14 | 1% | 55 | 47 | 45 | 237 | 99% |
| Radstock Kilmersdon Road Syphon emergency overflow Radstock Kilmersdon Road Syphon EO · WXW00593 | Wessex Water | 19.8 | 11 | 1% | 42 | 35 | 28 | 13 | 100% |
| WSX10153 WSX10153 | Wessex Water | 21.5 | 12 | 1% | – | – | – | – | – |
| Radstock Waterside storm overflow Radstock Waterside SO · WXW01197 | Wessex Water | 21.2 | 12 | 1% | 18 | 20 | 9 | 2 | 100% |
| Calne Inlet WXW00222 | Wessex Water | 46.5 | 26 | 1% | 56 | 38 | 21 | 44 | 100% |
| Calne storm tank overflow Calne Storm Tank · WXW00223 | Wessex Water | 46.3 | 26 | 1% | 58 | 72 | 26 | 256 | 100% |
| Coleford Kings Head WXW00596 | Wessex Water | 34.4 | 19 | 1% | 52 | 55 | 26 | 77 | 83% |
| Nunney storm tank overflow Nunney Storm Tank · WXW00816 | Wessex Water | 30.0 | 17 | 1% | 104 | 81 | 77 | 1,383 | 100% |
| Melksham Bath Road OFF Road F/O Scout Hall WXW00964 | Wessex Water | 21.8 | 12 | 1% | 83 | 81 | 56 | 512 | 100% |
| Lacock Nethercote Hill WXW00784 | Wessex Water | 29.3 | 16 | 1% | 12 | 11 | 6 | 21 | 100% |
| Midsomer Norton Berkeley Avenue storm overflow Midsomer Norton Berkeley Avenue SO · WXW00129 | Wessex Water | 22.5 | 12 | 1% | 53 | 49 | 28 | 58 | 100% |
| Midsomer Norton Welton storm overflow Midsomer Norton Welton SO · WXW01213 | Wessex Water | 21.7 | 12 | 1% | 6 | 13 | 7 | 1 | 100% |
| Nunney Market Place South END WXW00815 | Wessex Water | 30.8 | 17 | 1% | 6 | 0 | – | – | 100% |
| Midsomer Norton Northmead Road/ Hayes Park Road WXW00722 | Wessex Water | 23.4 | 13 | 1% | 19 | 20 | 17 | 68 | 100% |
| Edford storm tank overflow Edford Storm Tank · WXW00402 | Wessex Water | 36.6 | 20 | 0% | 97 | 61 | 46 | 366 | 100% |
| Norton St Philip storm tank overflow Norton ST Philip Storm Tank · WXW00812 | Wessex Water | 13.3 | 7 | 0% | 66 | 76 | 47 | 757 | 100% |
| Edford Inlet WXW00401 | Wessex Water | 36.6 | 20 | 0% | 77 | 68 | 46 | 219 | 100% |
| Calne Mosses Mill 2 WXW00758 | Wessex Water | 48.0 | 27 | 0% | 50 | 64 | 44 | 146 | 100% |
| WSX10136 WSX10136 | Wessex Water | 22.8 | 13 | 0% | – | – | – | – | – |
| WSX10034 WSX10034 | Wessex Water | 24.0 | 13 | 0% | – | – | – | – | – |
| Holt THE Star WXW01127 | Wessex Water | 16.0 | 9 | 0% | 70 | 82 | 48 | 254 | 100% |
| Great Somerford storm tank overflow Great Somerford Storm Tank · WXW00480 | Wessex Water | 55.3 | 31 | 0% | 73 | 95 | 52 | 334 | 100% |
| Witham Friary WXW01272 | Wessex Water | 39.0 | 22 | 0% | 36 | 37 | 17 | 163 | 100% |
| Calne Marden House Culvert AT Rear WXW00846 | Wessex Water | 49.3 | 27 | 0% | 25 | 32 | 10 | 34 | 94% |
| WSX10088 WSX10088 | Wessex Water | 14.1 | 8 | 0% | – | – | – | – | – |
| Calne Strand / Church Street WXW01128 | Wessex Water | 49.2 | 27 | 0% | 22 | 24 | 10 | 4 | 95% |
| Calne Mosses Mill 1 WXW00757 | Wessex Water | 48.0 | 27 | 0% | 0 | 1 | 0 | 0 | 100% |
| Trowbridge Rosecroft Polebarn Road WXW00863 | Wessex Water | 16.3 | 9 | 0% | 1 | 0 | 1 | 0 | 100% |
| Calne River Marden (River Bank) South Marden House NEW Road WXW00234 | Wessex Water | 49.2 | 27 | 0% | 2 | 6 | 1 | 1 | 100% |
| Calne Market Hill / Strand WXW00685 | Wessex Water | 49.2 | 27 | 0% | 2 | 2 | 0 | 0 | 100% |
| Calne Oxford Road / Wood Street WXW01278 | Wessex Water | 49.7 | 28 | 0% | 1 | 2 | 1 | 0 | 100% |
| Wingfield Church Lane WXW00282 | Wessex Water | 17.1 | 10 | <1% | 83 | 81 | 40 | 524 | 100% |
| Southwick Chantry Gardens WXW00246 | Wessex Water | 19.4 | 11 | <1% | 17 | 36 | 18 | 149 | 100% |
| Peasedown ST John Wellow Lane WXW01205 | Wessex Water | 16.6 | 9 | <1% | 0 | 0 | 0 | 0 | 100% |
| Clutton Greenbrook WXW00304 | Wessex Water | 25.2 | 14 | <1% | 39 | 32 | 28 | 120 | 100% |
| Stoke ST Michael Stoke Hill WXW01068 | Wessex Water | 38.3 | 21 | <1% | 1 | 11 | 1 | 7 | 99% |
| WSX10083 WSX10083 | Wessex Water | 25.5 | 14 | <1% | – | – | – | – | – |
| Clutton Maypole Farm WXW00699 | Wessex Water | 25.5 | 14 | <1% | 20 | 26 | 22 | 16 | 100% |
| Westbury storm tank overflow Westbury Storm Tank · WXW01235 | Wessex Water | 23.4 | 13 | <1% | 69 | 72 | 21 | 228 | 100% |
| Melksham Shaw C OF E School Playing Field WXW00980 | Wessex Water | 24.1 | 13 | <1% | 68 | 79 | 40 | 278 | 100% |
| Kilmersdon WXW00592 | Wessex Water | 22.2 | 12 | <1% | 39 | 54 | 28 | 154 | 100% |
| Dilton Marsh Inlet WXW00367 | Wessex Water | 27.8 | 16 | <1% | 72 | 65 | 31 | 274 | 100% |
| South Wraxall Home Farm Lower Wraxall storm tank overflow South Wraxall Home Farm Lower Wraxall Storm Tank · WXW01017 | Wessex Water | 25.3 | 14 | <1% | 32 | 44 | 12 | 165 | 100% |
| Ston Easton Wellow Brook IN Field Near BY WXW01110 | Wessex Water | 27.0 | 15 | <1% | 88 | 67 | 49 | 100 | 97% |
| Westbury Frogmore Road OPP 67 WXW00772 | Wessex Water | 23.4 | 13 | <1% | 39 | 42 | 25 | 20 | 100% |
| Hinton Blewett Inlet WXW00546 | Wessex Water | 27.6 | 15 | <1% | 48 | 45 | 43 | 114 | 100% |
| Midsomer Norton Cautletts Close WXW00238 | Wessex Water | 22.7 | 13 | <1% | 23 | 20 | 10 | 73 | 99% |
| Westbury Inlet WXW01234 | Wessex Water | 23.4 | 13 | <1% | 6 | 8 | 1 | 2 | 98% |
| Westbury West END O/S 36 WXW01221 | Wessex Water | 23.4 | 13 | <1% | 2 | 2 | 0 | 0 | 98% |
| Stratton on the Fosse storm tank overflow Stratton ON THE Fosse Storm Tank · WXW01079 | Wessex Water | 25.2 | 14 | <1% | 6 | 3 | 0 | 0 | 100% |
| Chapmanslade Divers Bridge WXW00369 | Wessex Water | 32.1 | 18 | <1% | 1 | 16 | 2 | 15 | 100% |
| WSX10031 WSX10031 | Wessex Water | 25.7 | 14 | <1% | – | – | – | – | – |
| Ston Easton Home Farm storm overflow Ston Easton Home Farm SO · WXW00559 | Wessex Water | 27.0 | 15 | <1% | 31 | 29 | 30 | 26 | 90% |
| Dilton Marsh PEN Knapp WXW00853 | Wessex Water | 27.3 | 15 | <1% | 1 | 5 | 1 | 3 | 100% |
| Frome Courts Barton Marston Lane WXW00693 | Wessex Water | 28.9 | 16 | <1% | 0 | 0 | 0 | 0 | 100% |
| Mells storm tank overflow Mells Storm Tank · WXW00710 | Wessex Water | 29.0 | 16 | <1% | 25 | 2 | 0 | 0 | 100% |
| Coleford storm tank overflow Coleford Storm Tank · WXW00308 | Wessex Water | 33.8 | 19 | <1% | 119 | 98 | 73 | 780 | 100% |
| Christian Malford Swalletts Gate WXW01093 | Wessex Water | 52.3 | 29 | <1% | 34 | 56 | 35 | 127 | 100% |
| Chippenham Gastons Road WXW00458 | Wessex Water | 37.8 | 21 | <1% | 82 | 76 | 46 | 191 | 100% |
| Trudoxhill WXW01156 | Wessex Water | 35.7 | 20 | <1% | 65 | 81 | 53 | 584 | 100% |
| Cranmore Inlet WXW00340 | Wessex Water | 35.7 | 20 | <1% | 84 | 60 | 37 | 422 | 100% |
| Calne Quemerford Bridge WXW00908 | Wessex Water | 51.5 | 29 | <1% | 46 | 49 | 12 | 45 | 97% |
| Chippenham Bristol Road WXW00184 | Wessex Water | 38.2 | 21 | <1% | 63 | 63 | 53 | 79 | 100% |
| Lyneham B Site Raf Lyneham storm tank overflow Lyneham B Site (Main STW) RAF Lyneham Storm Tank · WXW00915 | Wessex Water | 55.4 | 31 | <1% | 60 | 53 | 24 | 316 | 100% |
| Coleford Inlet WXW00307 | Wessex Water | 33.8 | 19 | <1% | 28 | 59 | 42 | 162 | 100% |
| Leigh on Mendip storm tank overflow Leigh ON Mendip Storm Tank · WXW00627 | Wessex Water | 33.4 | 19 | <1% | 38 | 35 | 16 | 195 | 100% |
| Wanstrow WXW01187 | Wessex Water | 36.8 | 20 | <1% | 29 | 27 | 16 | 123 | 100% |
| WSX10129 WSX10129 | Wessex Water | 24.1 | 13 | <1% | – | – | – | – | – |
| Dilton Marsh IN Field Behind 127 High Street WXW00366 | Wessex Water | 26.8 | 15 | <1% | 21 | 25 | 10 | 21 | 94% |
| Oakhill storm tank overflow Oakhill Storm Tank · WXW00818 | Wessex Water | 39.5 | 22 | <1% | 21 | 23 | 5 | 30 | 100% |
| Chippenham Dallas Road WXW00360 | Wessex Water | 37.5 | 21 | <1% | 0 | 0 | 0 | 0 | 100% |
| Gurney Slade WXW00490 | Wessex Water | 42.0 | 23 | <1% | 39 | 65 | 19 | 95 | 100% |
| Compton Bassett THE Pond WXW01125 | Wessex Water | 53.9 | 30 | <1% | 133 | 154 | 70 | 1,501 | 99% |
| Biddestone Manor Cottages WXW00679 | Wessex Water | 39.8 | 22 | <1% | 100 | 99 | 40 | 251 | 100% |
| Dauntsey THE Green WXW01120 | Wessex Water | 54.2 | 30 | <1% | 42 | 34 | 25 | 95 | 100% |
| Broads Green WXW00195 | Wessex Water | 51.5 | 29 | <1% | 109 | 116 | 54 | 1,058 | 100% |
| Calne Rough Leaze WXW00221 | Wessex Water | 52.8 | 29 | <1% | 34 | 36 | 23 | 396 | 100% |
| Tockenham Inlet WXW01141 | Wessex Water | 56.5 | 31 | <1% | 77 | 52 | 17 | 53 | 100% |
| Compton Bassett storm tank overflow Compton Bassett Storm Tank · WXW00317 | Wessex Water | 52.0 | 29 | <1% | 30 | 34 | 16 | 192 | 100% |
| WSX10149 WSX10149 | Wessex Water | 50.3 | 28 | <1% | – | – | – | – | – |
| Kington Langley WXW00601 | Wessex Water | 53.2 | 30 | <1% | 68 | 64 | 13 | 148 | 96% |
A dash: no annual return for that overflow in that year.
Sources and credits
Storm overflow annual returns: © Environment Agency copyright and/or database right 2025, Open Government Licence v3.0. Overflow positions: the water companies via the National Storm Overflow Hub, CC BY 4.0. River network: contains OS data © Crown copyright and database right 2026 (OS Open Rivers). Traced and weighted by SwimSignal (swimsignal.co.uk), whose method is at swimsignal.co.uk/methods.html. All credits and licences.