Derriton STW So Holsworthy
Storm overflow operated by South West Water. The source names Coles Stream (S) as the receiving water.
- 77
- Spills in 2025
- 321.9
- Recorded hours
- 99%
- Monitor operation
- 5
- Years listed
The reported spill count was 15 lower than in 2024. This compares event counts, not discharge volume.
Checking the latest monitor report…
How it compares in 2025
Derriton STW So Holsworthy recorded 77 spills in 2025. That is more than 95% of the 14,239 overflows in England with a reported figure, and ranks 565th nationally. Among South West Water overflows it ranks 172nd of 1,357; the median South West Water overflow recorded 21 spills. On the Deer waterbody it ranks 2nd of 4.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 77 | 321.9 |
| England | 565th of 14,239 | 11 | 22.3 |
| South West Water | 172nd of 1,357 | 21 | 39.4 |
| Deer | 2nd of 4 | 74.5 | 333.2 |
Rank 1 has the most spills. Equal counts share a rank. Only overflows with a reported count are ranked. Counts do not measure volume, so a higher rank does not mean more sewage.
Annual spill history
| Year | Spills | Duration | Monitor operation | Source |
|---|---|---|---|---|
| 2025 | 77 | 321.9 hours | 99% | Official data |
| 2024 | 92 | 483.8 hours | 100% | Official data |
| 2023 | 91 | 318.2 hours | 100% | Official data |
| 2022 | 49 | 132.7 hours | 100% | Official data |
| 2021 | 76 | 272.8 hours | 100% | Official data |
A missing figure means the source did not provide a usable value. A zero is shown as zero. Monitor operation below 90% can make comparison less reliable.
Outlet details
- Water company
- South West Water
- Outlet type
- Inlet storm overflow at a wastewater treatment works
- Permit
- NRA-SW-6975
- Activity reference
- A2
- Grid reference
- SS34020322
- Waterbody ID
- GB108047013880Official waterbody record ↗
- Location source
- Official annual grid reference
- Location precision
- About 10 metres
- Location note
- Unknown
About the name and type
The annual return lists this asset as “Inlet SO at WwTW”: inlet storm overflow at a wastewater treatment works. The overflow is at the inlet of a treatment works, where wastewater enters the works.
The waterbody link opens the Environment Agency record for the exact ID in the return. It is a source lookup; we do not import its classification.
Where it is
The recorded position is about 0.9 km south of the Holsworthy reference point in the ONS built-up areas data.
Area and water pages
Check the official record
Public access to this outlet is unknown. Do not enter restricted land or use this page as a route guide.
Open official source ↗Other outlet records nearby
- Derriton STW SSO HolsworthyCurrent status unknown
South West Water · Coles Stream (S)
- Westcroft CSO HolsworthyCurrent status unknown
South West Water · River Deer
- Dobles Lane SPS Pscsoeo HolsworthyCurrent status unknown
South West Water · Tributary River Deer (S)
- Dobles Lane Ind Est CSO HolsworthyCurrent status unknown
South West Water · Trib of River Deer
Questions about Derriton STW So Holsworthy
- Who operates Derriton STW So Holsworthy?
- South West Water is the operator named in the annual record. The permit reference is NRA-SW-6975.
- Where does Derriton STW So Holsworthy discharge?
- The source names Coles Stream (S) as the receiving water. This does not show how far a discharge travelled.
- How many times did Derriton STW So Holsworthy spill in 2025?
- The 2025 return records 77 counted spill events and 321.9 hours of recorded discharge. Spills are counted with the 12/24-hour method, so this is not a count of every start signal.
- Can I trust the 2025 figures for this outlet?
- The monitor worked for 99% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Derriton STW So Holsworthy discharging right now?
- This record is linked to a company live feed. The panel above shows the latest report we hold, with its date. That report can be old, and the monitor can be offline, so check the date before relying on it. A report that no discharge is taking place is not a water-quality result.
- How accurate is the map marker?
- The marker comes from the grid reference in the official annual return, which is accurate to about 10 metres. It shows the recorded outlet position, not the extent of any discharge.
- What kind of outlet is Derriton STW So Holsworthy?
- The annual return lists the asset type as “Inlet SO at WwTW”, which means inlet storm overflow at a wastewater treatment works. The overflow is at the inlet of a treatment works, where wastewater enters the works.
- How does Derriton STW So Holsworthy compare with other overflows?
- Derriton STW So Holsworthy recorded 77 spills in 2025. That is more than 95% of the 14,239 overflows in England with a reported figure, and ranks 565th nationally. Among South West Water overflows it ranks 172nd of 1,357; the median South West Water overflow recorded 21 spills. On the Deer waterbody it ranks 2nd of 4. Ranks compare counted spill events only. They do not compare volume or harm.
- Does zero spills mean the water was safe?
- No. A zero means the annual return recorded zero counted spill events for this outlet and year. It is not a water-quality test, and pollution can come from other sources.