Works & capacity
Every overflow drains to a treatment works that serves a fixed area. When a works is too small for the flow it receives, spills follow. This crosses each works' estimated load against its permitted flow â and against the spill record â to say what the numbers point to.
Capacity across the River Dart
4 of the 12 works we track are estimated to take more flow than their permit allows â between them they serve about 2,462 people. A further 5 cannot be assessed at all, because we have not found a permit or a population estimate for them.
The black line marks 100% of permitted dry-weather flow; a dashed empty bar means no permit was found to measure against. Load is an estimate â population served à per-head water use, plus infiltration â not a permit-compliance finding. A works over 100% here is a signal to investigate, not a proven breach. Overflow hours are the works' own storm overflow in the last full year.
5 works we cannot assess
For BUCKFASTLEIGH STW, RATTERY, ASHPRINGTON, DITTISHAM MAIN, STRETE we have no permit or no population estimate on record, so we cannot check whether the works is big enough. This is a gap in the public record â not a clean bill of health â and it is the quickest thing on this page to fix: the permitted flow is public information a water company must supply on request.
Why this matters for reading spills
Works over capacity
If a works cannot treat the flow it receives, it spills to protect itself. The remedy is capital investment or a lower permitted load â years and millions, but it is the water company's to fix.
Headroom, but upstream spills anyway
A works with spare capacity whose network still spills points upstream â a blockage, a failed pump, or groundwater getting into the sewer. Often cheap to fix, and fixable now.
No permit found
Where we cannot find the permitted flow, the works cannot be assessed at all. That is a gap in the public record, and closing it is the first step to holding capacity to account.
How growth becomes spills
A developer has a section 106 right to connect to the public sewer, and the water company has a section 94 duty to accept the flow â but capacity is only funded on a five-yearly capital cycle. New connections can therefore arrive years before the works is enlarged to take them, and the overflow absorbs the gap. Schedule 3 to the Flood and Water Management Act 2010, which would make sustainable drainage mandatory and give a SuDS Approving Body a say, has been in force in Wales since 2018 but remains uncommenced in England â so here there is no such body.
What the permit actually sets
The permitted dry-weather flow is set by Formula A â roughly DWF + 1,360 Ã population + 2 Ã trade effluent (litres/day). The permit also sets a flow to full treatment, typically about three times DWF, below which everything must be treated rather than spilled. Our load figure compares estimated demand against that permitted DWF. 2 works in the catchment publish no permitted flow at all, so their load cannot be calculated â they show as not assessed, never 0%.