Stamshaw Road Portsmouth CSO - 109337
Storm overflow operated by Southern Water. The source names Portsmouth Harbour as the receiving water.
- 3
- Spills in 2025
- 1.8
- Recorded hours
- 93.4%
- Monitor operation
- 2
- Years listed
Checking the latest monitor report…
How it compares in 2025
Stamshaw Road Portsmouth CSO - 109337 recorded 3 spills in 2025. That is more than 26% of the 14,239 overflows in England with a reported figure, and ranks 9,843rd nationally. Among Southern Water overflows it ranks 610th of 975; the median Southern Water overflow recorded 7 spills. On the Portsmouth Harbour waterbody it ranks 17th of 36.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 3 | 1.8 |
| England | 9,843rd of 14,239 | 11 | 22.3 |
| Southern Water | 610th of 975 | 7 | 17 |
| Portsmouth Harbour | 17th of 36 | 3 | 1.8 |
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 | 3 | 1.8 hours | 93.4% | Official data |
| 2024 | 9 | 13 hours | 88%Low coverage | 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
- Southern Water
- Outlet type
- Storm overflow on the sewer network
- Permit
- W00279
- Activity reference
- Storm
- Grid reference
- SU6407002560
- Waterbody ID
- GB580705140000Official waterbody record ↗
- Location source
- Official annual grid reference
- Location precision
- About 1 metres
- Location note
- Unknown
About the name and type
The annual return lists this asset as “SO on sewer network”: storm overflow on the sewer network. The return places this overflow on the sewer network.
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 1.3 km south-west of the Portsmouth 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
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- Newcomen Road Portsmouth CSO - 108460Current status unknown
Southern Water · Portsmouth Harbour
- Winstanley Road Portsmouth CSO - 108504Current status unknown
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- North End Avenue Portsmouth CSO - 108773Current status unknown
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Questions about Stamshaw Road Portsmouth CSO - 109337
- Who operates Stamshaw Road Portsmouth CSO - 109337?
- Southern Water is the operator named in the annual record. The permit reference is W00279.
- Where does Stamshaw Road Portsmouth CSO - 109337 discharge?
- The source names Portsmouth Harbour as the receiving water. This does not show how far a discharge travelled.
- How many times did Stamshaw Road Portsmouth CSO - 109337 spill in 2025?
- The 2025 return records 3 counted spill events and 1.8 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 93.4% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Stamshaw Road Portsmouth CSO - 109337 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 1 metres. It shows the recorded outlet position, not the extent of any discharge.
- What kind of outlet is Stamshaw Road Portsmouth CSO - 109337?
- The annual return lists the asset type as “SO on sewer network”, which means storm overflow on the sewer network. The return places this overflow on the sewer network.
- How does Stamshaw Road Portsmouth CSO - 109337 compare with other overflows?
- Stamshaw Road Portsmouth CSO - 109337 recorded 3 spills in 2025. That is more than 26% of the 14,239 overflows in England with a reported figure, and ranks 9,843rd nationally. Among Southern Water overflows it ranks 610th of 975; the median Southern Water overflow recorded 7 spills. On the Portsmouth Harbour waterbody it ranks 17th of 36. 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.