That's not what a lack of indoor plumbing is like though. In fact going camping when indoor plumbing exists isn't even the same: when it's a few enthusiasts digging holes sparsely is very different to when the entire population is doing it.
The first city to really hit this wall was London in 1858. When the river level dropped, the sewage in the Thames remained, resulting in "the great stink". Construction of a proper sewage system began the following year in 1859. In 1865 it was complete enough to begin operation. It wasn't considered complete until a decade later, in 1875.
The role of sewage in spreading cholera was first hypothesized in 1849 by John Snowe. He'd put together a pretty convincing case by 1854, and the actual bacteria was discovered in the same year. But the proof that finally convinced the medical establishment didn't come about until 1883.
If this makes you suspect that the medical establishment had their collective heads up their collective asses, I'm not about to disagree.
See the prolonged acceptance of bloodletting, resistance to handwashing, and on and on to the slow adoption in the present day of evidence based medicine.
If you don't know about the latter, see https://medicalxpress.com/news/2022-06-dont-medical-treatmen....
The more authority that you believe yourself to have, the stronger the cognitive dissonance against admitting to your mistakes.
Doctors feel themselves to have a lot of authority.
Also, I've seen people do amazingly dumb things because of disbelieving their doctors, so maybe a certain amount of overconfidence would be protective?
But that's because GPT-5 Mini's responses are strongly shaped by task framing and context. You can get it to say just about anything as long as you stay away from taboo areas.
It did refer me to a lot of books, and the ones I looked up did in fact actually exist, but none of them seemed to be relevant.
Sorry for not having given you an easier cookie crumb.
A single person might choose the internet over plumbing because at worst they have to compost and use an outhouse, which is less inconvenient than being locked out of most web services.
But while giving up the internet globally sends you to the 1980s, giving up plumbing globally sends you to the 1780s. YouTube and Amazon ain't worth chamberpots, dessicated skyscrapers, and regular cholera outbreaks that would reduce most cities into dysfunctional public health disasters.
Like a world without elevators, urban life without plumbing very quickly becomes unsustainable in buildings above a certain size.
Burning Man recommends 6 liters of water per day per person for bathing, cooking, drinking, etc.: https://burningman.org/event/preparation/playa-living/water/ But that can generally be cut in half when you're anywhere other than one of the world's driest deserts in the middle of summer. This means you need to bring in your own weight in water roughly once a month; if there's no elevator, and you can safely lift 25% of your own weight, you can lug it up the stairs once a week. If there's an elevator, you can probably bring the water up the elevator every month or two.
About a third of that water has to eventually go back down in the form of piss, which is not a major problem if you have sealable plastic bottles to store it in. There's always the risk of an unpleasant accident with that approach, of course, but that's rare.
So I don't think there's ever a building size where a lack of indoor plumbing makes urban life unsustainable. If you're strong enough to walk up and down the stairs every day, you're strong enough to carry water up the stairs once a week. If there's an elevator that you can ride carrying two children, you can also ride it carrying water, once a month. Throughout history, and today in poor rural areas, most people have always had to carry their water much farther than that.