Short answer: no single method covers every contaminant. Boiling deals with microorganisms but leaves — and concentrates — metals, salts and nitrate. Carbon filters target chlorine, taste and volatile compounds. Distillation separates water from substances that cannot evaporate with it. And some things, such as tritium, cannot be removed by any home method at all. If water is known to be chemically contaminated, health agencies say to use a different water source rather than treat it yourself.
What each method does
| Contaminant | Boiling | Typical carbon filter | Distillation |
|---|---|---|---|
| Bacteria, viruses, protozoa | Effective | Depends on the cartridge | Effective |
| Heavy metals (e.g. lead), salts, fluoride | No — concentration rises as water evaporates | Partial, cartridge-dependent | Left behind in the boiling chamber |
| Nitrate and nitrite | No — boiling concentrates nitrate | Usually not | Left behind in the boiling chamber |
| Volatile organic compounds, fuel components | Partial | This is what carbon is for | Can travel with the steam — an activated-carbon post-filter is needed |
| Cyanobacterial toxins (e.g. microcystins) | No — they are heat stable | Depends on the cartridge | Not volatile, so they stay in the chamber |
| Tritium (radioactive hydrogen in water) | No | No | No — it is chemically water itself |
Why boiling alone is not enough
Boiling is the classic answer to microbiological risk, and it works: the World Health Organization's guidelines credit bringing water to a rolling boil with a substantial reduction of bacteria, viruses and protozoa.
The problem is everything that does not evaporate. When you boil water in an open pot, some water leaves as steam and whatever was dissolved in it stays behind — in a smaller volume. The WHO notes explicitly that boiling increases nitrate concentration. The same logic applies to lead, arsenic and salts.
Two further cases are worth knowing. Cyanobacterial toxins from algal blooms are, in the WHO's words, "extremely heat stable" and resistant to boiling — which is why authorities issue "do not drink, do not boil" notices during blooms rather than boil-water notices. And in a study of Japanese tap water after 2011, boiling did not reduce iodine-131; concentrations rose as the volume fell.
What distillation separates — and what it doesn't
A distiller reverses the usual arrangement: instead of boiling water in the container you drink from, it boils water in one chamber, moves only the steam to a second container and condenses it there. Substances that cannot evaporate at that temperature simply never make the journey. That is why metals, salts, fluoride, nitrate and non-volatile toxins remain in the boiling chamber — visible, as owners who descale their units know.
The US emergency-preparedness site Ready.gov is unusually direct about this: in its water-treatment table, for removing heavy metals, salts and most other chemicals, boiling is marked "No", chlorination "No" and distillation "Yes".
The honest limits matter just as much:
- Volatile compounds can carry over. Substances that turn into gases easily, such as petrol components and some solvents, can travel with the steam unless the system is designed to capture them. This is precisely what an activated-carbon post-filter is for — Megahome distillers pass the condensed steam through one before it reaches the bottle.
- Tritium cannot be removed. Tritiated water is chemically water. The US Nuclear Regulatory Commission states that tritium "cannot be filtered out of the water"; the IAEA reported that it cannot be removed "by any other industrial scale system"; the WHO's guidelines list tritium as not possible to remove. It evaporates and condenses with the water, so distillation does not separate it either.
- Distillation is not a designated regulatory technology for radionuclides. In US drinking-water regulation, the listed best available technologies are ion exchange, reverse osmosis, lime softening and coagulation/filtration. Distillation's effect on non-volatile radioactive substances follows from the same physics as for metals and salts, but it is not a certified regulatory route, and no agency publishes a removal percentage for it.
When you should not treat water at home at all
This is the part most product pages leave out. The US Centers for Disease Control and Prevention states plainly that you cannot make water containing fuel, toxic chemicals or radioactive material safe by boiling or disinfecting it. The WHO's emergency technical note makes a parallel point: household treatment removes physical and microbiological pollution, but not chemical contamination.
So if a supply is known or announced to be chemically contaminated, the correct response is an alternative source — bottled or tankered water, or whatever your local authority directs — not home treatment. Follow the notice your water utility or health authority issues; it is specific to the substance involved.
If your water quality is uncertain, change the filter more often
The stainless-steel boiling chamber holds back non-volatile substances whatever state the carbon sachet is in. The activated-carbon post-filter is different: it captures volatile compounds that travel with the steam, and its capacity is used up faster when the feed water carries more of them. Megahome's guidance:
| Feed water | Replace the carbon sachet |
|---|---|
| Normal municipal tap water | As stated in your manual (in daily use, owners commonly change it about weekly) |
| Uncertain quality — well water, stored or tanked water, after a supply incident | Every 5 batches, i.e. every 20 litres |
| Known or strongly suspected contamination | After every 4-litre batch |
Rinse the boiling chamber after each batch and descale it with citric acid when scale appears; residue concentrates there by design.
Key takeaways
- Boiling addresses microorganisms but concentrates metals, salts and nitrate.
- Distillation separates water from non-volatile substances; official emergency guidance from Ready.gov lists it for heavy metals, salts and most chemicals where boiling and chlorination are marked "No".
- Volatile compounds can travel with steam, which is why a carbon post-filter is part of the system — and why it should be replaced more often when water quality is uncertain.
- Tritium cannot be removed by any home method, and distillation is not a designated regulatory technology for radionuclides.
- If water is known to be chemically contaminated, use an alternative supply and follow your local authority.
Frequently asked questions
Does boiling water remove lead or nitrate?
No. Boiling reduces microorganisms but does not remove dissolved metals or nitrate; as water evaporates, their concentration rises.
Can a distiller remove radioactive substances?
Non-volatile substances stay in the boiling chamber — the same physics that keeps metals and salts behind. But distillation is not a designated regulatory technology for radionuclides, no agency publishes a removal percentage for it, and tritium cannot be removed by any method because it is chemically water.
What about algal toxins during a bloom?
The WHO describes microcystins as extremely heat stable, so boiling does not destroy them. Authorities normally advise not to drink the water at all during such events — follow that notice.
How often should I change the carbon filter?
Follow your manual for normal tap water. If the water is of uncertain quality, Megahome recommends every 5 batches (20 litres); with known contamination, after every 4-litre batch.