The Thames at Ham and Kingston Is Now a Designated Bathing Water — What That Actually Means for Swimmers

From May 2026, the stretch of the Thames at Ham and Kingston becomes an officially designated bathing water site. It sounds like a green light to dive in. But the reality is considerably more complicated — and residents who swim here deserve to know exactly what this status does and does not guarantee.

What Designation Actually Means

Designated bathing water status is granted by the Department for Environment, Food and Rural Affairs (DEFRA) following an application process. It does not mean the water has been declared safe. What it means is that the Environment Agency (EA) is now legally required to test the water quality at this location regularly throughout the bathing season — which runs from 15 May to 30 September each year.

Those tests measure levels of two specific bacteria: Escherichia coli (E. coli) and intestinal enterococci. Based on the results gathered over multiple seasons, the EA assigns one of four classifications: Excellent, Good, Sufficient, or Poor. A newly designated site has no classification yet. That rating will only emerge after seasons of data collection.

In plain terms: the site now has a monitoring framework. It does not yet have a clean bill of health.

What Testing Looks Like in Practice

During the bathing season, the EA takes water samples at the designated point — typically at least fifteen times across the season, though frequency can increase around pollution events. Results are published on the EA's Swimfo website, usually within a few days of sampling.

Critically, the EA also issues short-term pollution risk forecasts. When heavy rainfall is predicted — or has just occurred — the system can flag elevated risk, because storm events routinely push untreated or partially treated sewage and surface water runoff into the river. On those days, a 'pollution risk warning' appears on Swimfo. Swimmers are advised not to enter the water.

This is not a theoretical concern on the Thames in Kingston. It is a regular occurrence.

The Hogsmill Problem Has Not Gone Away

The Hogsmill River flows through the Royal Borough and discharges into the Thames close to the newly designated bathing stretch. It has a documented history of sewage pollution — from both storm overflow discharges operated by Thames Water and from misconnected pipes that allow foul water into the surface drainage system.

Thames Water operates combined sewer overflows (CSOs) on the Hogsmill. These are legally permitted to discharge diluted sewage during heavy rainfall to prevent sewage backing up into homes. In practice, campaigners and environmental groups including the Hogsmill Valley Partnership have recorded discharges occurring far more frequently than 'exceptional rainfall' conditions might justify.

Designation of the Thames stretch as a bathing water does not compel Thames Water to accelerate investment in Hogsmill infrastructure. It does not automatically reduce CSO frequency. What it does do is create a formal, public record of water quality that makes pollution events harder to ignore — and harder for water companies and regulators to minimise.

What the Council's Responsibilities Are

Kingston Council is not the water quality regulator — that is the EA's role. But designation creates a set of responsibilities that sit with the local authority nonetheless.

The council must designate the bathing water site with appropriate signage, including information about the classification (once one is assigned) and current-season water quality data. It is required to display this information at the bathing site itself during the season.

The council also has a role in managing the land around the site — including surface water drainage, any land-based pollution sources, and public facilities. If dog fouling, surface runoff from nearby land, or misconnected drainage is contributing to poor water quality, these are matters the council has powers to address.

There is also a less formal but important role: advocacy. The council can — and arguably should — use the designation as leverage in conversations with Thames Water and the EA to accelerate improvements to the Hogsmill and to push for reduced CSO discharges. Whether Kingston Council will do this robustly remains to be seen.

The Questions Residents Should Be Asking

Designation is a genuine milestone. It is the result of campaigning by local wild swimming groups and environmental advocates, and it should be acknowledged as such. But scrutiny is warranted on several fronts.

What is the council's plan for signage and public information? Residents swimming here from May 2026 need real-time access to pollution warnings, not just a notice board updated weekly.

Has the council mapped all pollution sources in the catchment? Misconnected pipes — where household foul drainage is incorrectly plumbed into surface water drains — are a known contributor to river pollution and are notoriously underreported. What active survey work is Kingston Council doing?

What formal representations has the council made to Thames Water about Hogsmill CSO discharges? If the answer is 'none', or 'we have written a letter', that is not enough for a stretch of river where people are now encouraged to swim.

What facilities will be provided at the site? A designated bathing water with no changing facilities, no showers, and no accessible entry points is a designation in name only for many residents.

What happens if the site is classified 'Poor' after its first rated season? Under the Bathing Water Regulations 2013, a site rated Poor for five consecutive years faces closure of the designation. The council needs a remediation plan before that scenario arises, not after.

A Landmark Moment — With Strings Attached

This is genuinely good news for Kingston and Ham. Having an officially monitored bathing water on the Thames gives residents real data, creates public accountability for water companies, and signals that wild swimming in urban rivers is a legitimate activity that deserves infrastructure and protection.

But designation is a starting line, not a finish line. The Hogsmill still discharges. Thames Water's investment timelines remain uncertain. And the council's role in championing water quality improvements — rather than simply welcoming a positive headline — is still to be demonstrated.

Residents who swim here, or who want to, deserve answers to the questions above before the season opens in May 2026.

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Want to put these questions directly to your local councillors? Kingston has 48 councillors across 19 wards — and with full council elections on 7 May 2026, every one of them is accountable to you right now. Use Council Clarity to find your ward councillors and send them a message asking what Kingston Council is doing to protect water quality at the newly designated bathing site. It takes two minutes, and councillors are required to respond.