I thought people might be interested in how a story such as this one comes together... back in April we published a piece looking at the specific issue of misconnections in one corner of London. But the volunteers working on the River Brent and River Crane in west London, who have been doing the leading work highlighting this issue, say it was hard to make people comprehend the scale of the problem.
The issue is you just see stories about "thousands of properties leaking sewage" and none it feels real.
I challenged Rachel Rees, who spent most of this year working for London Centric, to find a single example of a misconnected pipe and trace its journey through the capital. This became one of the most infuriating projects we've done. Endless formal requests for information, tracing underground rivers, trying to convince authorities that we are trying to highlight an issue and get individuals to confront it. She had to put up with constant nagging from me to keep going. Eventually she found this location in Crouch End and managed to follow its journey across north and east London.
All in all this was an absolutely crazy amount of work over eight months to bring this single story to life.
Rachel has since left to join a niche news publication called the "Financial Times", having picking up a nomination for young journalist of the year for her work with London Centric. So this is probably her final byline here — and it's one of those that I'm really proud to publish.
I may be wrong, but judging by the photo and the map, I think the point where the Moselle flows in to the Lea may be in Markfield Park. If so, it's close to this:
- one of the first sites in the city's modern wastewater-treatment system. Which is either apt or ironic, or possibly both. I'd not heard of the place until earlier this year when a friend suggested we visit. It's fascinating and highly recommended, especially on one of the days where the engine is working.
This article really struck me, particularly the idea of misconnections as a form of constant, low-level pollution that’s almost designed to evade detection.
It made me wonder whether this is a problem better approached the way lightning monitoring has been: not with a few perfect sensors, but with many cheap ones.
I’ve written a follow-up exploring the idea of a citizen-science sewage monitoring network built around simple ESP32 devices — and, crucially, a London-wide schools project that could combine education, data and river recovery (with water companies as sponsors rather than adversaries).
Important piece. Is there any data on whether this is something that’s solely new buildings that are the main cases, or are things like loft conversions that are part of this - where the plumbing may need to run in pipes to the sewage system separate from the rest of the property
Bit of a mix. In theory should be pretty hard for a new build to manage it but very much does happen.
With an extension you can see how it happens - stick a new bathroom on the back, you’re on a budget/builder is dodgy, they plumb it in and the issue becomes someone else’s problem.
Happened to a friend recently. New downstairs loo and extension. A few months later all the houses in the area with recent planning applications get a letter. They went to each recently installed loo and flushed dye down it to find the culprit. He was the unlucky one. Builders had to dig up the floor to fix it, but at least they did it!
Thames Water (in London at least) identifies properties that are misconnected, and writes to homeowners to let them know (then goes to councils if homeowners don’t fix it).
But it’s inevitably a hugely undiscovered problem — the process of finding misconnections is so long winded, and depends on volunteers literally wading through local waterways, like Ben from Clean Up the River Brent, who we spoke to for the article we did on this topic back in April or so. That’s why there’s such a mismatch between the reported numbers of misconnections and the much, much higher estimated real figures (eg Thames Water’s estimate that 1 in 10 properties in the area it covers are misconnected)
Great article Jim, but Croyden? Please, that's my home town. You'll have to decide whether to fire the subeditor or the graphics person. Oh, hang on...
Noooo we love all our Croyden readers. And also we defend Carly at all costs, she makes the articles look lovely, it’s on me to double check for the typos. Thanks for flagging, I’ll get her to fix that and I’ll upload a new version when done.
Wouldn’t the obvious solution be cutting the water supply to properties until the issue is resolved?! You wouldn’t be allowed to drive around a car leaking oil (I assume! Idk, I don’t drive!)
Nb is Haringey the worst performing LB per household? There are others with higher absolute numbers.
Haringey is the worst performing borough for live cases referred to the council - ie it has the highest number that Thames Water have identified, informed homeowners/council about, and that are still left unresolved.
It’s a slightly different metric to some of the other numbers mentioned, which are the number identified by Thames Water in that borough in the last 5 years (and hopefully in at least some cases, then fixed by homeowners)
In an internal report we obtained, Thames Water identified Haringey (anonymised but revealed through an foi) as the worst performer in this regard, taking “very little action” against misconnections
I did this reporting months ago, and told the council then that I knew about the property on Park Road that was misconnected. The fact that it is still misconnected now speaks volumes…
That internal Thames Water report also noted that one misconnection in London had been identified back in 2008 - and at the time of the report (early 2025 I think) was still releasing untreated sewage into the wrong sewer — and local waterways as a result
Legal bases can be changed. I didn’t mean to say ‘people should be punished by having their water cut off’ - clearly in many cases owners and residents are not even aware. But if we wanted to eliminate sewage being discharged, it would be very easily done by cutting water supply until problems are resolved and presumably that would speed up action.
I thought people might be interested in how a story such as this one comes together... back in April we published a piece looking at the specific issue of misconnections in one corner of London. But the volunteers working on the River Brent and River Crane in west London, who have been doing the leading work highlighting this issue, say it was hard to make people comprehend the scale of the problem.
The issue is you just see stories about "thousands of properties leaking sewage" and none it feels real.
I challenged Rachel Rees, who spent most of this year working for London Centric, to find a single example of a misconnected pipe and trace its journey through the capital. This became one of the most infuriating projects we've done. Endless formal requests for information, tracing underground rivers, trying to convince authorities that we are trying to highlight an issue and get individuals to confront it. She had to put up with constant nagging from me to keep going. Eventually she found this location in Crouch End and managed to follow its journey across north and east London.
All in all this was an absolutely crazy amount of work over eight months to bring this single story to life.
Rachel has since left to join a niche news publication called the "Financial Times", having picking up a nomination for young journalist of the year for her work with London Centric. So this is probably her final byline here — and it's one of those that I'm really proud to publish.
Great reporting thank you! It‘s exactly stories like this one which show why London needs proper news reporting.
Excellent journalism, a sincere thank you for this.
Really excellent work. I wonder if Feargal Sharkey has read this?!
Yet more excellent work. Thanks hugely.
I may be wrong, but judging by the photo and the map, I think the point where the Moselle flows in to the Lea may be in Markfield Park. If so, it's close to this:
https://www.mbeam.org/
- one of the first sites in the city's modern wastewater-treatment system. Which is either apt or ironic, or possibly both. I'd not heard of the place until earlier this year when a friend suggested we visit. It's fascinating and highly recommended, especially on one of the days where the engine is working.
Yes, it is in Markfield Park! That’s very ironic, thanks for flagging, I hadn’t known about the history
Fantastic reporting! Thank you ☃️
This article really struck me, particularly the idea of misconnections as a form of constant, low-level pollution that’s almost designed to evade detection.
It made me wonder whether this is a problem better approached the way lightning monitoring has been: not with a few perfect sensors, but with many cheap ones.
I’ve written a follow-up exploring the idea of a citizen-science sewage monitoring network built around simple ESP32 devices — and, crucially, a London-wide schools project that could combine education, data and river recovery (with water companies as sponsors rather than adversaries).
Here’s the piece if anyone’s interested:
👉 https://richardvahrman.medium.com/listening-to-londons-sewers-549e596a69be
Thanks for shining a light on a problem that’s literally underground.
Important piece. Is there any data on whether this is something that’s solely new buildings that are the main cases, or are things like loft conversions that are part of this - where the plumbing may need to run in pipes to the sewage system separate from the rest of the property
Bit of a mix. In theory should be pretty hard for a new build to manage it but very much does happen.
With an extension you can see how it happens - stick a new bathroom on the back, you’re on a budget/builder is dodgy, they plumb it in and the issue becomes someone else’s problem.
Happened to a friend recently. New downstairs loo and extension. A few months later all the houses in the area with recent planning applications get a letter. They went to each recently installed loo and flushed dye down it to find the culprit. He was the unlucky one. Builders had to dig up the floor to fix it, but at least they did it!
Fair play to that council, bad luck to your mate!
I'm local to lordship rec and the sewage stink is really awful. Thanks for looking in to it. really vile
How can a homeowner discover if their property is misconnected?
Thames Water (in London at least) identifies properties that are misconnected, and writes to homeowners to let them know (then goes to councils if homeowners don’t fix it).
But it’s inevitably a hugely undiscovered problem — the process of finding misconnections is so long winded, and depends on volunteers literally wading through local waterways, like Ben from Clean Up the River Brent, who we spoke to for the article we did on this topic back in April or so. That’s why there’s such a mismatch between the reported numbers of misconnections and the much, much higher estimated real figures (eg Thames Water’s estimate that 1 in 10 properties in the area it covers are misconnected)
None in Southwark. Should I feel better, or does it mean they haven’t started on Southwark yet?
Great article Jim, but Croyden? Please, that's my home town. You'll have to decide whether to fire the subeditor or the graphics person. Oh, hang on...
Noooo we love all our Croyden readers. And also we defend Carly at all costs, she makes the articles look lovely, it’s on me to double check for the typos. Thanks for flagging, I’ll get her to fix that and I’ll upload a new version when done.
Wouldn’t the obvious solution be cutting the water supply to properties until the issue is resolved?! You wouldn’t be allowed to drive around a car leaking oil (I assume! Idk, I don’t drive!)
Nb is Haringey the worst performing LB per household? There are others with higher absolute numbers.
Haringey is the worst performing borough for live cases referred to the council - ie it has the highest number that Thames Water have identified, informed homeowners/council about, and that are still left unresolved.
It’s a slightly different metric to some of the other numbers mentioned, which are the number identified by Thames Water in that borough in the last 5 years (and hopefully in at least some cases, then fixed by homeowners)
In an internal report we obtained, Thames Water identified Haringey (anonymised but revealed through an foi) as the worst performer in this regard, taking “very little action” against misconnections
I did this reporting months ago, and told the council then that I knew about the property on Park Road that was misconnected. The fact that it is still misconnected now speaks volumes…
That internal Thames Water report also noted that one misconnection in London had been identified back in 2008 - and at the time of the report (early 2025 I think) was still releasing untreated sewage into the wrong sewer — and local waterways as a result
Rachel lives! Listen to the woman who now knows more than almost any other journalist about London's suburban sewer system!
I don't think there is a legal basis for disconnecting residential properties because of a misconnection.
Legal bases can be changed. I didn’t mean to say ‘people should be punished by having their water cut off’ - clearly in many cases owners and residents are not even aware. But if we wanted to eliminate sewage being discharged, it would be very easily done by cutting water supply until problems are resolved and presumably that would speed up action.