Heol Plas Isaf Storm Overflow
Sign in to saveStorm overflow run by Dwr Cymru Welsh Water, discharging into Nant Mwrwg.
"Not discharging" means the company's monitor reports no discharge right now — not that the water is clean. The feed publishes status only; no discharge volume is measured.
Year by year
Dŵr Cymru Welsh Water's annual Event Duration Monitoring return to Natural Resources Wales (12/24-hour spill count), as compiled by The Rivers Trust. 2026 is our own running count, the same way, from the live feed since 23 September (when we began keeping every discharge it reports) — so it can only be lower than the full year. The feed reports only each overflow's latest discharge, so a discharge it moved past before we saw it end is counted as one spill with no hours: the hours are a floor. The official figure is published next spring.
"No data" means the monitor was not working or not required to report that year — not zero.
Discharges we have recorded
797 discharge periods since 8 Jan 2020, 1 whose end the feed never gave. 784 of them come from Dwr Cymru Welsh Water's own event-duration-monitoring records (published by the company, Jan 2020 – Dec 2025); the live feed adds anything after that. The official annual count is the figure to quote.
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15 min
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15 min
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not captured
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15 min
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11 h 30 min
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2 h 15 min
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1 h 15 min
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15 min
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30 min
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3 h 0 min
Show 30 earlier (of 797)
| Started | Ended | Discharge time |
|---|---|---|
| 1 h 45 min | ||
| 1 h 45 min | ||
| 15 min | ||
| 45 min | ||
| 15 min | ||
| 1 h 15 min | ||
| 9 h 0 min | ||
| 15 min | ||
| 16 h 30 min | ||
| 45 min | ||
| 15 min | ||
| 2 h 15 min | ||
| 15 min | ||
| 15 min | ||
| 15 h 30 min | ||
| 2 h 15 min | ||
| 15 min | ||
| 11 h 15 min | ||
| 15 min | ||
| 15 min | ||
| 11 h 30 min | ||
| 4 h 45 min | ||
| 1 h 0 min | ||
| 2 h 30 min | ||
| 20 h 0 min | ||
| 15 min | ||
| 6 h 15 min | ||
| 45 min | ||
| 30 min | ||
| 15 min |
The year figures above use the EA's 12/24-hour counting method, so they are comparable with the official figures; the monitor log's 966 raw blocks were merged into 797 continuous discharge periods (gaps under 15 min joined).
Look back by date
Discharge records held: 1 Jan 2020 to 31 Dec 2025 and from 24 Sep 2026. Choose the dates of a flood or a storm to see every discharge recorded then.
Days run midnight to midnight, UK time, up to 366 days at a time. A discharge beside rain or a flood is a timing match, not proof of cause, and no volume is published.
What the feed showed
FloodRadar's own record of every change of state Dwr Cymru Welsh Water's live feed has shown for this overflow, kept since : 12 states. The feed publishes its status now and its latest discharge, nothing older; the discharges above are read from this. It is here so the figures can be checked.
Show the last 12 states
| Seen | Status | Since | Latest discharge |
|---|---|---|---|
| Not discharging | → | ||
| Discharging | → no end yet | ||
| Not discharging | → | ||
| Discharging | → no end yet | ||
| Not discharging | → | ||
| Not discharging | → | ||
| Discharging | → no end yet | ||
| Not discharging | → | ||
| Discharging | → no end yet | ||
| Not discharging | → | ||
| Discharging | → no end yet | ||
| Not discharging | → |
Rain nearby last 30 days
Nearest live rain gauge: Bynea Raingauge, 3.6 km away. Brown shading = when this overflow was discharging; ▼ = a discharge start.
Overflow shading is a timing match, not proof of cause — heavy rain and spills share a trigger. Times come from the water company’s event-duration monitor (site status only; no discharge volume is published).
Where it is
Tell me when this overflow discharges
One message when the company's monitor reports a new discharge here. At most one every 6 hours.
Setting this alert needs JavaScript. The alerts you already have are on your alerts page.
The alert repeats the monitor's status: whether the overflow is discharging, not how much or why. It can only tell you about a discharge that starts after you turn it on.
Concerned about this overflow?
Report pollution you can see or smell to the regulator straight away; the company handles complaints about the overflow itself.
Live status: © Dŵr Cymru Welsh Water, from its Storm Overflow Map. Spill-event history: © Dŵr Cymru Welsh Water's published EDM start/stop records. Annual figures: The Rivers Trust EDM compilation, © Dŵr Cymru/Welsh Water, Open Government Licence. Times are shown in UK local time. FloodRadar republishes the monitor's status; it does not measure discharges itself.