Water Distillation: How It Works
Distillation boils water, collects steam, and re-condenses it — leaving behind most dissolved solids, heavy metals, and biological contaminants.
Removes
- • Heavy metals (lead, arsenic, mercury)
- • Nitrates
- • Bacteria and viruses
- • Fluoride
- • Most dissolved solids
- • Radium
Does Not Remove
- • Volatile organic compounds (VOCs evaporate with water)
- • Chlorine and chloramine
- • Some pesticides
How Distillation Purifies Water: The Phase Change Method
Water distillation mimics the natural water cycle — evaporation and condensation — in a controlled environment. Source water is heated to boiling (100°C / 212°F). Water molecules evaporate and rise as steam. The steam travels through a cooling coil or chamber where it re-condenses as purified liquid water. Dissolved contaminants that cannot evaporate at water's boiling point remain behind in the boiling chamber as scale and concentrated residue.
This phase change is extremely effective at removing dissolved inorganic compounds: minerals, heavy metals, nitrates, fluoride, bacteria, and viruses all remain in the boiling chamber. Lead boils at 1749°C — it cannot follow the water vapor. Bacteria and viruses are killed by the boiling temperature before they could volatilize. The limitation: volatile organic compounds (VOCs) that evaporate below or near 100°C can carry over into the condensate along with water vapor.
Where Distillation Wins: Applications RO Cannot Match
CPAP and PAP humidifiers
CPAP manufacturers require distilled water in humidifier chambers. Mineral deposits from tap or RO water build up in the heated chamber and can harbor bacteria. Distilled water eliminates mineral accumulation. RO water at 10-20 ppm TDS still forms deposits over time.
Laboratory and scientific equipment
Autoclaves, analytical instruments, and laboratory reagent preparation require water below 0.1 microsiemens/cm conductivity (essentially zero dissolved ions). High-quality distillers with a post-carbon polishing stage approach this level. RO alone does not.
Reef tanks and sensitive aquariums
Marine reef aquariums require near-zero TDS to allow precise control of synthetic seawater chemistry. RO/DI (deionized) units are the standard for this application — RO removes 90-97% of TDS, then a DI resin stage brings it to essentially zero. Pure distillation achieves similar TDS at lower per-gallon volume.
Steam irons and steam cleaners
Mineral scale destroys steam iron soleplate vents and steam cleaner components. Distilled or RO/DI water prevents scale entirely. Tap water, even softened, eventually scales steam equipment.
5-Year Cost: Distillation vs RO
| Cost Factor | Distiller (Waterwise 4000) | RO (iSpring RCC7AK) |
|---|---|---|
| System cost | $270 | $249 + $150 install = $399 |
| Electricity/year (2 gal/day) | $350–$470 | ~$15 |
| Filter/consumables/year | $30–$50 (cleaning) | $65–$80 |
| Annual operating total | $380–$520 | $80–$95 |
| 5-year total | $2,170–$2,870 | $799–$875 |
| Cost per gallon (2 gal/day) | $0.52–$0.79 | $0.06–$0.10 |
Distillation: Right for Specific Applications, Wrong for Daily Drinking Water
Top Products Using This Technology
Tap Score Essential City Water Test
aquasana
$179
- ✓EPA-certified lab
- ✓Tests 111 contaminants
Tap Score Well Water Test
aquasana
$239
- ✓EPA-certified lab
- ✓Tests 130 contaminants specific to well water
Clearly Filtered Water Pitcher
clearly filtered
$90+ $140/yr
- ✓NSF P473 certified — removes 99.9% of PFAS
- ✓Removes fluoride (unusual for a pitcher)
SpringWell CF1 Whole-House Carbon Filter
springwell
$1,197
- ✓1 million gallon capacity
- ✓9 GPM flow rate — no pressure loss