If you live somewhere the tap water is reliably safe, it is easy to assume that “water safety” is a solved problem with a few exceptions. The numbers say otherwise: about one person in four does not have drinking water that is on-premises, available when needed, and free from contamination.
This matters more than ever to people who move between countries — remote workers, expats, long-stay travellers, and anyone running a household in Southeast Asia, Latin America or sub-Saharan Africa. The useful question is not “is the water safe here” but “which failure mode am I dealing with, and what actually addresses it”.
The baseline
WHO and UNICEF’s Joint Monitoring Programme, 2025 report, with data running to 2024, puts it at 2.1 billion people — one in four — without safely managed drinking water, including 106 million who drink directly from untreated surface water. “Safely managed” is a strict definition: on-premises, available when needed, and free from contamination. Fail any one and you are outside the count.
Sanitation is measured alongside it: 3.4 billion people lack safely managed sanitation, including 354 million practising open defecation. Faecal contamination of source water is a well-established pathway to drinking-water risk, though the two statistics measure different things.
In fragile contexts, safely managed drinking-water coverage is 38 percentage points lower than in other countries, and least-developed countries are more than twice as likely to lack even basic drinking water. Coverage in urban areas has also stagnated, according to the same report.
What failure looks like: cholera
Cholera is the clearest visible signal that a water system has broken down. As of 29 June 2025, the WHO African Region reported 20 countries affected, 144,665 cases and 2,917 deaths — a case fatality rate of 2.0%. Five countries (South Sudan, DRC, Angola, Ethiopia and Mozambique) accounted for 92.3% of cases.
Fatality rates in cholera outbreaks are shaped largely by how quickly people reach treatment — which is a function of the health system around them, not of the pathogen alone.
The money and the leakage
UN-Water’s GLAAS 2025 report, covering 105 countries, found an average financing gap of roughly 46% among countries with comparable data, and non-revenue water close to 40% in some systems — leakage, poor asset management, weak billing.
That figure echoes our South Africa piece, with one important distinction. South Africa’s 47% is non-revenue water — a mix of physical loss and water delivered but never billed — against an international average its regulator puts at about 30%. GLAAS describes close to 40% in some systems, which is a different claim from a global average, and the two should not be blended together.
Cities that ration, and cities that sink
Two recent cases show how fast a capital’s water position can move.
In April 2024, about 10 million residents of Bogotá were put on water rationing with 24-hour cuts every ten days as reservoirs hit record lows — described as the most drastic measure the city had taken in decades.
Mexico City’s main storage system shows how far a capital’s water position can swing. Conagua reported in October 2025 that the Cutzamala system held 97.3% of capacity — 762 million cubic metres — supplying more than 5.5 million people and about 23% of the Valley of Mexico’s water.
The useful lesson is that storage is not the same variable as safety. If you want the specific record-low figures and the “Day Zero” discussion, read them from Conagua’s own reporting rather than a summary — we are only citing what we could verify in the October 2025 release.
The lesson is not “the crisis ended”. It is that storage is not the same variable as safety. A reservoir at 26% and one at 97% can both produce compliant water; what changes is source mix, treatment load, and the taste in your glass.
Jakarta tells a different story — one about pipes. PAM Jaya says coverage rose from just over 60% when it resumed full public control in 2023 to about 82% in 2026, targeting universal piped water by 2029. Excessive groundwater extraction, not sea-level rise, is described as the main cause of subsidence of up to 15 cm per year, with some areas down as much as 4 metres since the 1970s.
Treat the 82% as a utility claim rather than a measured connection rate — the article itself presents it as PAM Jaya’s figure. Where piped water is absent, people drill — and drilling is what sinks the city.
The contaminant travellers miss
Pathogens get all the attention, but some of the most consequential contaminants in the regions above are geological, not faecal.
A peer-reviewed study of northern Argentina found arsenic in drinking water varying from less than 1 to about 200 µg/L, with one source (San Antonio de los Cobres) fluctuating between 140 and 220 µg/L across ten years with no downward trend — against a WHO guideline of 10 µg/L. High groundwater arsenic is documented across the Puna, Chaco, Córdoba and Pampas regions.
Two details make this worth knowing. First, the study was published in 2006, so read it as evidence of a documented regional hazard rather than current concentrations. Second, and more importantly: boiling does not remove arsenic. Boiling kills pathogens and concentrates everything dissolved, because the water leaves as steam and the salts stay. The same is true of nitrate.
A layered approach, rather than a single product
The honest answer for uncertain supply is layering, matched to the failure mode:
- Sediment — rust, grit, tank debris. Cheapest stage, protects everything after it.
- Carbon — chlorine, taste, odour, some organics. Does not remove arsenic, nitrate, or make water microbiologically safe.
- Microbiological treatment — boiling, UV, or a certified hollow-fibre/ceramic element. This is a disinfection problem, and it is separate from filtration.
- Reverse osmosis — the stage that addresses dissolved contaminants including arsenic and nitrate, where the supply warrants it. It rejects a lot of water and needs pressure, so it suits a fixed installation more than a backpack.
- Portable treatment — for travel and emergencies, a filter bottle is a pathogen barrier, not a chemical one.
If you are setting up a household somewhere with intermittent or uncertain supply, a whole-house sediment and carbon system plus a drinking-water stage at the kitchen covers most of it, with disinfection handled separately. If you are travelling, a filter bottle covers pathogens and taste but not arsenic — which is exactly the gap most people do not know they have.
Portable & countertop · Under-sink systems · Whole house systems
Sources
- WHO/UNICEF JMP 2025 summary (2.1 billion without safely managed water) — who.int
- WHO African Region cholera bulletin, June 2025 — afro.who.int
- UN-Water GLAAS 2025 summary (financing gap, non-revenue water) — waterdiplomat.org
- BBC on Bogotá water rationing — bbc.com
- Conagua on Cutzamala storage, October 2025 — gob.mx/conagua
- The Diplomat on Jakarta piped water and subsidence — thediplomat.com
- Peer-reviewed study of arsenic in northern Argentina — pmc.ncbi.nlm.nih.gov