Want to avoid swimming in sewage? There’s an app for that

Before we get into the details of the app though, and how it can be used to make informed decisions about when to get into the water, a quick recap about why it’s necessary... In Scotland as in the rest of the UK, our sewers are set up as what’s known as a “combined system” – that is, both surface water (ie. rainfall) and sewage water travel through the same pipes before arriving at a treatment plant. When the system becomes overloaded and there’s a risk of sewage backing up into people’s homes – for example, during times of heavy rainfall – water companies are permitted to use Combined Sewer Overflows (CSOs) to discharge untreated sewage into rivers and seas. That all sounds fair enough – given a choice between raw sewage being pumped into the sea or raw sewage sloshing around on their bathroom floor, most people would take option A. However, SAS point out that CSOs are only supposed to be an emergency measure, and legislation states they should only be used under “exceptional circumstances.” ​Yet, based on the data​, it seems exceptional circumstances have somehow become the norm.

A few weeks ago, I met Henry Swithinbank, senior policy and advocacy manager at SAS, and he talked me through some of the 60-page SAS Water Quality Report for 2025. One passage in particular from the section on Scotland stands out: “In 2024,” it says, “Scottish Water recorded 23,498 [CSO] discharges for a total of 208,377 hours, but these figures are from only 6.7 per cent of their total network. Scotland has the highest average discharge rate per CSO of any water company [in the UK] at a whopping 89.3. So the real number of discharges [given there are 4,080 SCOs nationwide] could be as high as 364,629.”

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If Scotland’s CSOs are discharging raw sewage into rivers and seas 89.37 times per year on average, that means they’re doing it (on average) about once every four days. Can something happening once every four days be described as “exceptional circumstances”? If so, then I suppose today must be exceptional, being a Thursday, as Thursdays only come along once a week.

Semantics aside, the broader point is that raw sewage is being discharged into Scotland’s rivers and seas far more frequently than anyone would ideally like. The ultimate goal of Surfers Against Sewage is to continue to highlight the issue until our ailing sewage system is sorted out, but clearly that’s something that will take many years to achieve. In the meantime, SAS reason, the best way of keeping water users safe is to make them aware of any potential dangers from sewage pollution – which is where the Safer Seas and Rivers Service​ comes in.

After downloading the app and creating a “watch list” of places around the country where I might conceivably go surfing, the first alert I received was for Belhaven Bay near Dunbar. “Dunbar (Belhaven) has been affected by sewage discharge,” it said,​ alongside a little graphic of a turd with a red cross through it, “discharged from a sewer overflow at 03:34 on 06/10/2025.” It occurred to me that, for a discharge from the CSO near Belhaven to happen there must have been some sort of heavy rainfall event in the last day or two, so I visited the Scottish Environment Protection Agency (SEPA) website and checked out their handy Rainfall Data for Scotland map. According to this, as of 9am on 7 October, the 36 hour rainfall total for Dunbar was... 1mm.

Now, if 1mm of rainfall in 36 hours is enough to max out Dunbar’s sewage network then may the saints preserve them come November, when the real rain starts. It seems more likely, though, that this particular sewage spill was caused by something other than rainfall. From the perspective of a water user, the cause doesn’t really matter – what matters is that evidently relying on the old “stay out of the water after heavy rainfall and you'll be fine” mentality isn’t always enough. As of now, your best protection against getting sick is to download the SAS app.

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The kinds of illnesses you can pick up from water contaminated with sewage range from eye and ear infections to ​hepatitis and E.coli. Proving that a surfer or swimmer suffering from one of these ailments did indeed pick it up in the sea is obviously tricky. However, the SAS website now features a database of some 6,794 health reports from people all around the UK who at the very least appear to have become ill after coming into contact with contaminated water. One of these is Shelley Sim, a member of a wild swimming group who​ ​experienced stomach pains and fatigue after swimming at Belhaven Bay. She ended up spending a week in hospital ​with ​cryptosporidiosis. “I’m no longer swimming every day,” she told SAS​, ​”and I’m more cautious about getting into the water”. ​Reliably clean bathing water may still be a long ​way off, but in the meantime at least the new SAS app will make​ life easier for Sim and other water users like her.

For more on the Safer Seas and Rivers Service for Scotland see www.sas.org.uk/updates/scotlands-first-sewage-alerts-live-on-app/