Testing SwimSignal this winter

From 19 October 2026 to 28 February 2027 a small group of swimmers, paddlers and river groups are using SwimSignal and telling Ethan where it helps and where it is wrong. This page is for them. Thank you for taking part.

What the site claims

• For each spot, the chance that sewage from a monitored storm overflow upstream reaches it, today and for the next four days, from the water companies' live overflow data, the rain forecast and the river network. The level is low, moderate, high or very high.
• Which overflows upstream are discharging right now, and which matter most for the spot.
• At a designated bathing water, the Environment Agency's yearly rating and its sampler's latest algae check, with dates.
• On rivers, an estimate of the chance a water sample would fail the E. coli limit. It was tested on Environment Agency samples from May to September. From October to April nothing tests it, so over the winter it is shown with a dagger (†) and does not set the level.

What it does not claim

• That the water is clean or safe. "Low" means nothing the site looks at flags the day. Farm runoff, misconnected drains, boats, wildlife and unmonitored outfalls are invisible to it.
• Anything about currents, river height, cold water, weirs or depth.
• The Environment Agency's short-notice advice against bathing after a pollution incident or an algal bloom. A bathing water's page links to the EA's page, which has it.
• Live status for the Welsh overflows that affect the Dee and the Wye. Dŵr Cymru publishes none; those overflows are forecast from rain and their yearly record only.

Expect the forecast to be wrong some of the time. Every forecast is scored afterwards against what the overflows did, on the accuracy page, including where it was wrong.

What to do

1. Open a spot you know and press Save. Your saved spots sit at the top of the list and on the Saved page, with their five days side by side.
2. Before a swim, check the spot's page. Pick a day in the strip to see what set that day's level: the overflows, the rain, the water-quality estimate.
3. At the water, compare. Did the river look, smell or run the way the forecast suggested? Was there a known spill the site missed, or a red day that looked fine?
4. If you use a phone, add SwimSignal to your Home Screen (the steps are at the bottom of the home page). On an iPhone, alerts work only in the Home Screen app; on the Saved page you can turn them on for your saved spots. Alerts are new and untested on real phones, so say if one is late or never comes.
5. After two or three weeks, send your notes. Short and blunt is best.

What to tell us

Any of these, in your own words, through the feedback page (it prepares an email for you to send; no account):

• Did the forecast change where, when or whether you swam? Once is enough to say so.
• What did you not understand, or have to read twice?
• What did you distrust, and why?
• What was missing that you wanted before deciding?
• Which spot, and which day, when you report a miss. The spot's page has a "Copy link to this spot" button, and a day picked in the strip is in the link.

If you have your own water-sample results, Ethan would like to score the forecast against them too, and will share what comes out.

How your feedback is handled

The feedback page prepares an email on your device and sends nothing until you send it. Your email goes to hello@swimsignal.co.uk, read by Ethan only. Notes from testers are kept privately and only summarised findings are published, with no names. Please leave health details and other sensitive information out. The privacy notice has the rest.

What happens after

At the end of February the test decides what comes next. If at least five testers say the site changed a decision, it launches publicly in late April 2027, before the bathing season opens on 15 May. If fewer do, the presentation is fixed first. Either way, the testers hear the result.

Contact

Ethan Buckley, hello@swimsignal.co.uk. SwimSignal is a free, non-commercial project run by one person; the About page says how it works and who is behind it.

For a pollution concern right now, use the Environment Agency's incident line (0800 80 70 60) and local advice. SwimSignal is not an emergency service.