| ISC | Elevated Chlorate Results – Tresco | Chlorate > 700 ug/l for multiple samples | 4 | 14485.36 |
| UUT | Warrington and Liverpool T&O Event | Point source pollution of the River Dee with 2-isopropyl-3-methoxypyrazine (IPMP) from a dairy farm | 4 | 5840.28 |
| ISC | Elevated Chlorate Results – Buzza SR | Chlorate > 700 ug/l for two samples | 4 | 5067.812 |
| SST | Hampton Loade – Elevated Propyzamide | Raw water deterioration | 4 | 2997.422 |
| SES | Cheam – Temporary cessation of Softening | Treatment failure upstream of final disinfection | 1 | 1435.06 |
| SST | High THM – Aldridge | Plant failure – Failure – Disinfection System | 4 | 918.795 |
| UUT | Cheshire and Merseyside Customer Contacts | Raw water deterioration | 4 | 465.128 |
| SRN | Dunkirk BPT Ingress | Structural failure – Service reservoir | 4 | 315.857 |
| ISC | Precautionary Boil Advice – Coliform Detections – Bryher, Isles of Scilly | Microbiological Contamination – Treatment works | 4 | 256.448 |
| ANH | Welton WTW – Post UV – Detection of Clostridium perfringens | Microbiological Contamination – Treatment works | 4 | 160.177 |
| SRN | Testwood WSW Plant failure & LOS | Planned work – Company staff | 4 | 154.959 |
| SRN | Brede WSW High Chlorate | Planned work – Company staff | 4 | 134.473 |
| SRN | Wingham WSW-Nitrates above PCV | Raw water deterioration | 4 | 114.658 |
| ANH | Welton WTW – Detection of Clostridium perfringens | Microbiological Contamination – Treatment works | 3 | 97.197 |
| SRN | Hastings LOS | Mains problem/ damage – Mains – Burst | 4 | 80.684 |
| TMS | Animal Ingress in Farnborough Service Reservoir | Structural failure – Service reservoir | 3 | 62.767 |
| SST | 20″ Burst Main – Leabrook Road Wednesbury | Mains problem/ damage – Mains – Burst | 1 | 53.599 |
| SVT | Chester Taste and Odour | Raw water deterioration | 4 | 45.798 |
| SES | Cheam Loss of Supply | Failure of the contact tank outlet valve in the closed position following an unplanned works shutdown resulted in the inability to discharge treated water from the works. | 1 | 34.016 |
| ANH | Little Melton WTW E. Coli | Microbiological Contamination – Treatment works | 3 | 33.186 |
| SWB | Summercourt Burst Main | Mains problem/ damage – Mains – Burst | 1 | 29.548 |
| SRN | Testwood WSW – Enterococci detection | Microbiological Contamination – Treatment works | 4 | 27.903 |
| SRN | South Hill WSR Foreign Object | Other – Specify Below: Small lamp left in tank after inspection. Removed by ROV. | 1 | 27.815 |
| WSX | Langport White Water | Mains problem/ damage – Mains – Burst | 4 | 26.075 |
| ANH | Boughton Reservoir 3 – repeat coliforms | Microbiological Contamination – Treatment works | 3 | 23.929 |
| TMS | Reading Loss of supply | Loss of heating leading to freezing of assets. The event was prolonged due a run-to-waste decision that was based on a miscommunication over presence of a disinfectant residual and the lack suitable pumps to fulfil the run-to-waste decision. | 4 | 20.265 |
| SWB | Aerated Water Contacts in Truro Area | Emergency Work | 3 | 18.856 |
| SRN | Easton WSW Loss of Supplies following chlorine gas leak | Plant failure – Failure – Disinfection System | 3 | 18.648 |
| SRN | Twyford WSR Nitrate above PCV | Raw water deterioration | 3 | 18.122 |
| SRN | Baldslow WSR Ingress | Structural failure – Service reservoir | 4 | 17.481 |
| CAM | Euston WTW – Breach of disinfection | Plant failure – Failure – Disinfection System | 4 | 17.382 |
| CAM | Euston WTW – Breach of disinfection requirement | Plant failure – Failure – Disinfection System | 4 | 17.382 |
| WSX | Poole Trunk Main Burst | Mains problem/ damage – Mains – Damage by Third Party/Unknown | 1 | 15.761 |
| SEW | Cookham WTW Nitrate | Raw water deterioration | 4 | 15.612 |
| SWB | Media interest in Woodgreen supply zone | Raw water deterioration | 4 | 14.525 |
| SRN | Testwood Industrial Clostridium perfringens Detection | Unclear. some issues with PAC dosing, RGF operation and possible ingress, but no definitive cause. | 4 | 13.952 |
| SRN | Dyke Road Brighton WSR No1. Ingress | Structural failure – Service reservoir | 4 | 12.406 |
| SRN | Wigmore 2 WSR Tank Ingress | Structural failure – Treatment works | 4 | 11.414 |
| YKS | Longwood WTW loss of ferric dosing | Plant failure – Failure – Pumps | 4 | 11.316 |
| YKS | Middlestown/Horbury discolouration | Mains problem/ damage – Mains – Burst | 3 | 10.518 |
| WSX | Danesborough SR2 Enterococci | Satisfactory investigation, did not identify root cause | 2 | 9.036 |
| UUT | South Cheshire Discolouration | Discoloured water – cause unknown at present | 2 | 8.682 |
| NES | Tow Law Discolouration | Planned work – Company staff | 4 | 8.451 |
| LNW | Sufficiency of supplies – Park Views Epsom | Unplanned shut down of Cheam works on 15 December 2024, due to a faulty valve on the outlet of the contact tank | 3 | 8.301 |
| SRN | Brede WSW Harland Tank Ingress | Structural failure – Treatment works | 4 | 8.068 |
| IWN | Ebbsfleet – Water Outage | Leak located however valves on site not in fully open positions, causing low flows. | 1 | 7.795 |
| TMS | Media Interest in Beckenham, BR3 | Increased illness contacts following publication of an article by the Guardian relating to water quality | 1 | 7.565 |
| IWN |
Newmarket Road Do Not Use
| Ground Contamination / Spillage – Hydrocarbon | 4 | 7.416 |
| TMS | Ufton Nervet WTW Turbidity Issue | Emergency Work | 4 | 7.08 |
| BRL | Frampton Cotterell discolouration | Planned work – company staff | 3 | 6.73 |
