Halwill STW So Halwill
Storm overflow operated by South West Water. The source names (S) River Carey as the receiving water.
- 85
- Spills in 2025
- 1,014.1
- Recorded hours
- 100%
- Monitor operation
- 5
- Years listed
Checking the latest monitor report…
How it compares in 2025
Halwill STW So Halwill recorded 85 spills in 2025. That is more than 96% of the 14,239 overflows in England with a reported figure, and ranks 421st nationally. Among South West Water overflows it ranks 140th of 1,357; the median South West Water overflow recorded 21 spills.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 85 | 1,014.1 |
| England | 421st of 14,239 | 11 | 22.3 |
| South West Water | 140th of 1,357 | 21 | 39.4 |
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 | 85 | 1,014.1 hours | 100% | Official data |
| 2024 | 110 | 1,491.4 hours | 88.5%Low coverage | Official data |
| 2023 | 121 | 1,788.3 hours | 61.5%Low coverage | Official data |
| 2022 | 180 | 1,510.4 hours | 100% | Official data |
| 2021 | 133 | 962.2 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
- 2027
- Activity reference
- A2
- Grid reference
- SX42959914
- Waterbody ID
- GB108047008040Official 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 1.5 km south-west of the Halwill Junction 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
- Ashwater STW So AshwaterCurrent status unknown
South West Water · (S) River Carey
- Clawton STW So ClawtonCurrent status unknown
South West Water · Tributary of River Claw(S)
- St Giles O T Heath SPS Pscsoeo St GilesCurrent status unknown
South West Water · Tributary of the River Tamar
- Lifton STW So LiftonCurrent status unknown
South West Water · River Thrushel
Questions about Halwill STW So Halwill
- Who operates Halwill STW So Halwill?
- South West Water is the operator named in the annual record. The permit reference is 2027.
- Where does Halwill STW So Halwill discharge?
- The source names (S) River Carey as the receiving water. This does not show how far a discharge travelled.
- How many times did Halwill STW So Halwill spill in 2025?
- The 2025 return records 85 counted spill events and 1,014.1 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 100% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Halwill STW So Halwill 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 Halwill STW So Halwill?
- 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 Halwill STW So Halwill compare with other overflows?
- Halwill STW So Halwill recorded 85 spills in 2025. That is more than 96% of the 14,239 overflows in England with a reported figure, and ranks 421st nationally. Among South West Water overflows it ranks 140th of 1,357; the median South West Water overflow recorded 21 spills. 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.