After the third lockdown ended, in that summer when everyone felt faintly broken, we ran away to the sea. At first it rained torrentially. But then the sun began tentatively to come out, and my son went snorkelling in a hidden rocky cove near the Cornish cottage we had rented. When the next day he started being violently sick, my first thought was food poisoning. But the whole family had eaten the same food, and the only one to fall ill was the lone swimmer. And that’s how I learned, after all these years of happily swimming in British rivers and seas, just how filthy they have become. That’s why, as a family, we no longer go near the water after heavy rain (the most likely time for sewers to be overwhelmed, and for emergency storm overflows to respond by dumping sewage into waterways). It’s why we have a faintly depressing new holiday routine of waking up and checking the Surfers Against Sewage app – which logs all the latest discharges around the coast – before heading to the beach, and why for paddleboarding at home I follow a Twitter account that sends alerts whenever Thames Water dumps something unmentionable in Oxfordshire’s rivers. Swimming in the cool green under the willows on a hot summer’s day, overlooked by nothing but passing swans, is one of those small free joys that everyone should try once in life. But nothing ruins the romance of the water’s edge like the feeling you may be playing bacterial Russian roulette, which helps explain why of all the issues at play in the current local election campaign, sewage seems rather unexpectedly to be bubbling to the top. Tory MPs are still getting angry letters, and in some cases vitriolic abuse on social media, a year and a half after being whipped to vote against an opposition amendment that would have imposed a legal duty on water companies to stop sewage entering rivers. (In vain have they insisted that they aren’t against cleaner water in principle, and that the amendment was simply badly drafted.) But what’s unusual is that the outrage cuts across traditional political divides, uniting everyone from laidback surfers to retired pillars of the community living in seaside towns who worry that the beaches aren’t safe for their visiting grandchildren. Born-again wild swimmers, evangelical about the mental health benefits of cold water, are naturally up in arms. But so are lifelong environmentalists, anglers, owners of tourist businesses dependent on the sea, and people who are none of those things but see in these murky waters another sign of national decline. Like waiting a week and a half for a GP appointment or getting stuck in a tailback at Dover, worrying about your children swimming in effluent this summer engenders a very strong sense of a country sliding backwards, unable to manage even the basic functions we once took for granted. Why does everything about Britain suddenly feel so threadbare, so shoddy, so crumbling at the edges? Ministers are clearly well aware of the deeper emotions water pollution stirs up, with polling suggesting that 68% of voters think the government is handling it badly and the Liberal Democrats staging an indignant series of local election photo opportunities on chilly beaches. The environment secretary, Thérèse Coffey, this week launched the second government initiative in a year to tackle water pollution. In fairness to her, this problem didn’t begin on her watch. But it evidently isn’t going to end there, either, judging by the contents of the package: regulators will have new powers to impose unlimited fines on water companies for polluting waterways, but there’s scepticism about whether they will be used. And while threatening higher fines implies it’s something the water companies could stop tomorrow if they really wanted to, the truth is more complicated. Galling as it is to watch highly paid water company executives rewarding themselves for failure, this mess is the collective responsibility of industry, regulators and governments over decades – and won’t be solved by one of them alone. Floating filth may be the symptom, but the root cause of polluted waterways is underinvestment in Britain’s elderly sewerage system, built for Victorian times and increasingly unable to cope with the demands of a vastly bigger population. (Although the number of recorded sewage spills fell last year, according to the Environment Agency that’s largely due to the hot dry weather meaning fewer storms, rather than some kind of concerted action.) A defensive Coffey argued that the problem couldn’t be solved overnight because upgrading sewers would add hundreds of pounds to customers’ bills in the middle of a painful cost of living crisis. But why does the government seemingly think the only answer to a failure of vital national infrastructure is to load the cost on to people who are already struggling? Whatever happened to funding public goods from a mixture of progressive taxation and private sector investment, as ministers seemingly have no hesitation in doing with projects such as high-speed rail or superfast broadband? Water hasn’t really been a political issue in my lifetime, but that’s changing. Rising global temperatures spell an increasingly water-stressed future, in which Britain will need – as Coffey rightly suggested – to build more reservoirs, fix more leaks, use less water and generally stop thinking of ourselves as a soggy island where, if anything, it rains too much. But we’ll also need to take more care of our precious waterways, and recognise that critical infrastructure consists not just of the shiny toys beloved of legacy-seeking prime ministers, but also the unglamorous stuff hidden beneath our feet. The Victorian brick-lined tunnels through which much of London’s sewage still runs were originally built in response to what became known as the Great Stink. In the hot summer of 1858, the stench of rotting human effluent in the Thames grew so bad that curtains in the Houses of Parliament were soaked in chloride of lime in an effort to block the smell – believed at the time to cause disease. The Times recorded that MPs had been “forced by sheer stench” to tackle a problem they’d avoided until it washed up on their very doorstep. Thankfully, we no longer live in an era of open sewers running down East End streets, and the Thames is not yet reduced to what the then Conservative chancellor Benjamin Disraeli called a “Stygian pool reeking with ineffable and intolerable horrors”. One thing, however, does hold true down the centuries: clean water is a basic human right. But as with all rights, sometimes it can only be secured by kicking up a great big stink. Gaby Hinsliff is a Guardian columnist