Boiling kills microorganisms — full stop. It partially removes free chlorine (slowly), barely touches chloramine, and does not remove fluoride, PFAS, lead or nitrates at all. Because boiling evaporates water while non-volatile contaminants stay behind, it actually leaves those contaminants slightly more concentrated. If your goal is anything other than disinfection, boiling is the wrong tool.
The quick answer table
| Contaminant | Does boiling remove it? | What happens |
|---|---|---|
| Bacteria, viruses, protozoa | Yes | Destroyed at a rolling boil — this is what boiling is for |
| Free chlorine | Partially | Volatile; off-gasses over several minutes of boiling |
| Chloramine | Barely | Far more stable than chlorine; boiling removes it very slowly |
| Temporary hardness | Partially | Some precipitates as kettle scale; permanent hardness remains |
| Fluoride | No — concentrates | Non-volatile ion; stays behind as water evaporates |
| PFAS | No — concentrates | Extremely heat-stable; unaffected by boiling |
| Lead & heavy metals | No — concentrates | Non-volatile; concentration rises as volume falls |
| Nitrates | No — concentrates | Non-volatile; same concentration effect |
| Sediment | No | Boiling does not filter particles |
What boiling actually does
Boiling is a disinfection method. A rolling boil destroys bacteria, viruses and protozoa reliably, which is why utilities issue boil-water notices after contamination events — and for that job, nothing beats it for simplicity. Chemically, though, boiling can only do two things: drive off compounds that are volatile (evaporate readily), and evaporate the water itself. Anything dissolved in the water that isn’t volatile — minerals, fluoride, PFAS, metals, nitrates — simply stays behind in a shrinking volume of water. That’s why boiling concentrates most contaminants rather than removing them.
Chlorine and chloramine — the one partial win
Free chlorine is volatile, so extended boiling (several minutes, not just reaching the boil) will drive most of it off — faster than letting a jug stand overnight, which also works. The catch for most Australians: the majority of capital-city supplies now use chloramine, not free chlorine — Sydney, Brisbane, Adelaide, Melbourne’s west, and parts of Perth among them. Chloramine was chosen by utilities precisely because it’s more stable and persistent than chlorine, and that stability means boiling removes it very slowly — impractically slowly for a kettle. If chloramine taste is your complaint, the effective fix is catalytic carbon filtration, not heat. Check which disinfectant your city uses in our water quality lookup.
Fluoride
Fluoride is added to Australian supplies at roughly 0.6–1.0 mg/L and exists in water as a dissolved ion. Ions don’t evaporate with steam — so when you boil water, the fluoride stays in the pot while the water leaves as vapour. Boil a litre down by 20% and the fluoride concentration has risen by roughly a quarter. If reducing fluoride is your goal, only reverse osmosis or activated alumina do the job meaningfully — our fluoride removal guide covers what works and what doesn’t.
PFAS
PFAS chemicals are famous for one property above all: they are extraordinarily stable. The carbon–fluorine bonds that make them “forever chemicals” in the environment also make them completely indifferent to your kettle — they neither break down nor evaporate at boiling temperature. As with fluoride, boiling concentrates them slightly. Meaningful PFAS reduction requires certified activated carbon (NSF/ANSI 53 with PFAS scope) or reverse osmosis (NSF/ANSI 58). Our PFAS in Australian drinking water guide covers where it’s found and which filters are actually certified for it.
Lead, nitrates and heavy metals
Same chemistry, same answer: lead, copper, nitrates and other dissolved metals are non-volatile and are concentrated, not removed, by boiling. This one matters most for infant formula — boiling water sterilises it for mixing, but if the underlying water had elevated nitrates or lead, boiling makes that slightly worse, not better. For anything metallic, the fixes are certified carbon-block (lead, NSF 53) or reverse osmosis; our baby formula water guide covers the infant-specific detail.
What works instead
Match the tool to the problem: microorganisms — boiling or UV. Chlorine taste — any decent carbon filter. Chloramine — catalytic carbon specifically. Fluoride — reverse osmosis or activated alumina. PFAS — certified carbon or RO. Hardness/scale — TAC conditioning or a softener (boiling only moves the scale from your pipes to your kettle). Our filter types guide maps each technology to what it removes, and the Find My Filter quiz turns your situation into a shortlist.