Thames Water · overflow TWL00571
Monitor offline
Recorded by the operator as Dollis Brook. The outfall is 4 m from the River Brent on the Ordnance Survey river network, which is the river this page groups it under.
The Environment Agency data shows this overflow's monitor (operator listed as Thames Water) as offline (status timestamp in the public data: 15 Sept 2026 at 03:00 UTC); while offline the data cannot show whether it is spilling.
📍 51.57464°, -0.22482°
2
spill events
1h
cumulative discharge
1.2 h
longest single event
2026-06-04
first event on record
In the last 30 days this overflow recorded 0h of discharge. Thames Water has 44 of its 577 monitored overflows reporting spills in this 30-day window.
9 other overflows discharge into the Dollis Brook. 1 has its monitor offline. Combined recorded discharge in the last 30 days: 2h.
No spill events recorded in the last 30 days.
What the water company itself reported to the Environment Agency’s annual returns for this overflow, year by year. Hours are the total reported discharge duration; monitor working is the share of the year the event monitor was operating (a figure of 0% may mean no usable monitoring data rather than no spills). These figures are the operator's own reporting, not our measurement, and our live record above begins on 6 May 2026.
| Year | Spills counted | Hours | Monitor working | Matched by |
|---|---|---|---|---|
| 2024 | 10 | 5h | 99% | hub id |
| 2025 | 11 | 5h | 100% | hub id |
2024, the operator's stated reason: "High spill threshold not met"
2025, the operator's stated reason: "High spill threshold not met"
Source: Environment Agency, Event Duration Monitoring storm overflow annual returns, all years. Matched to this overflow by hub id.
Latest readings at the Environment Agency gauge "Brent Cross", on the River Brent, which is 0.6 km from this overflow.
These are the Environment Agency's own gauge readings at the named station, shown for context. The station measures the river, not this overflow, and a reading does not show whether a discharge occurred or was permitted. Trend compares the latest reading with the one nearest 24 hours earlier; a change of 5% or less is shown as steady. How we keep the record.
TH-PBRR0070 · FRESHWATER - RIVERS
758 m away · last tested 9 days ago
TH-PBRR0094 · FRESHWATER - RIVERS
1.5 km away · last tested 10 weeks ago
TH-PBRR0007 · FRESHWATER - RIVERS
2.8 km away · last tested 10 weeks ago
TH-PGWB0003 · FRESHWATER - BATHING WATER
4.3 km away · last tested 5 weeks ago
TH-PGWB0001 · FRESHWATER - BATHING WATER
4.6 km away · last tested 5 weeks ago
TH-PGWB0002 · FRESHWATER - BATHING WATER
4.9 km away · last tested 5 weeks ago
The record above is verifiable from public Environment Agency and water-company data. Three official accountability channels — pre-filled with the evidence on this page.
If you can see foam, sewage debris, dead fish, or smell something wrong — submit a citizen report. Confirmed reports are added to the Truth Engine and strengthen the public record on this overflow.
📷 Report what you saw →The official complaints route. Most companies require submission through their web form rather than email — open the form, then paste the pre-filled letter.
Subject: Storm overflow TWL00571 on the Dollis Brook: request for information Dear Thames Water, I am writing about storm overflow TWL00571 on the Dollis Brook. Environment Agency storm overflow monitoring data for overflow TWL00571 on the Dollis Brook (operator listed as Thames Water) records no spill events starting between 18 September 2026 and 18 October 2026. As of 18 October 2026 at 11:34 UTC, the monitor for this overflow is reported as offline (status timestamp in the public data: 15 September 2026 at 03:00 UTC). While a monitor is reported offline, the public data cannot show whether the overflow is spilling. Further details from the public record: - Open automated data flags on River Truth for this overflow: 1 (comparisons between public datasets, not findings of fault) - On the River Brent, per the OS Open Rivers network (Ordnance Survey, Open Government Licence) - Location: 51.57464, -0.22482 - Sources: Environment Agency National Storm Overflow Hub and Water Quality Archive (Open Government Licence v3.0), cross-referenced via River Truth (https://rivertruth.co.uk/overflow/4112) These figures are taken from public monitoring data as published and may be revised by the publisher. They are not a finding that any permit condition has been breached. [Add your personal context here, for example how you use this stretch of water.] Please could you tell me: 1. Whether the monitoring record summarised above is accurate and complete 2. Why the monitor is reported as offline and when it is expected to report again 3. What work, if any, is planned at this overflow, and on what timeline 4. What measures are in place to reduce spills from this overflow in future [Delete if not applicable: I have copied the Environment Agency, Ofwat and my MP into this correspondence.] Yours faithfully, [Your name] [Your address] [Your customer reference if you are a Thames Water customer]
This overflow sits in the Hendon constituency — currently represented by David Pinto-Duschinsky (Labour). Click below to open WriteToThem with the letter copied to your clipboard — paste it into the message box.
Prefer to write to the MP for where you live? Enter your postcode and we'll redirect WriteToThem accordingly.
Subject: Constituent query: storm overflow TWL00571 on the Dollis Brook Dear [your MP, WriteToThem will fill this in], I am writing as your constituent about public storm overflow monitoring data for our area. Environment Agency storm overflow monitoring data for overflow TWL00571 on the Dollis Brook (operator listed as Thames Water) records no spill events starting between 18 September 2026 and 18 October 2026. As of 18 October 2026 at 11:34 UTC, the monitor for this overflow is reported as offline (status timestamp in the public data: 15 September 2026 at 03:00 UTC). While a monitor is reported offline, the public data cannot show whether the overflow is spilling. Further details from the public record: - Open automated data flags on River Truth for this overflow: 1 (comparisons between public datasets, not findings of fault) - On the River Brent, per the OS Open Rivers network (Ordnance Survey, Open Government Licence) - Location: 51.57464, -0.22482 - Sources: Environment Agency National Storm Overflow Hub and Water Quality Archive (Open Government Licence v3.0), cross-referenced via River Truth (https://rivertruth.co.uk/overflow/4112) These figures are taken from public monitoring data as published and may be revised by the publisher. They are not a finding that any permit condition has been breached. [Add your personal context here, for example how you and your family use this stretch of water.] I would like to ask: 1. Whether you support strengthening the regulatory regime for storm overflows, and monitor coverage in particular 2. Whether you would raise the monitoring data for this overflow with the Secretary of State for Environment, Food and Rural Affairs, the Environment Agency or Ofwat Yours sincerely, [Your name] [Your address (WriteToThem requires a postal address to verify your constituency)]
MP details are looked up live from the UK Parliament Members API under the Open Parliament Licence v3.0. River Truth makes no claim about this MP's voting or advocacy record on water issues — they are shown solely as the elected representative for this constituency.
For active pollution incidents — dead fish, foam, sewage on the riverbank — the EA hotline operates 24/7 and triggers a recorded investigation.