A water distiller copies the natural water cycle on your kitchen counter: it boils water, lets the steam rise away from dissolved minerals, metals and microbes, cools that steam back into liquid, and passes it through an activated-carbon filter into a collection bottle. Because it separates water by changing its state rather than straining it, distillation removes the vast majority of impurities — although a few volatile compounds that boil like water can travel with the steam, which is exactly why the carbon post-filter is there.
What is distillation, in one sentence?
Distillation separates substances by their boiling points. Water turns to steam at 100 °C at sea level; dissolved salts and metals such as calcium, magnesium, sodium and lead do not evaporate at that temperature, so when the water leaves as vapour, they stay behind. It is the same principle that makes rain fresh even though much of it evaporated from salty seas.
What happens inside a water distiller, step by step?
A countertop distiller such as the Megahome MH-943TWS works in four stages, with no plumbing or installation — you fill it, close the lid and switch it on.
- Boil. You pour about 4 litres of tap water into the stainless-steel boiling chamber. A 565 W heating element under the chamber brings the water to a rolling boil and keeps it there. Sustained boiling also kills or inactivates bacteria, viruses and parasites in the water.
- Evaporate. Steam rises into the stainless-steel steam dome. Minerals, metals, salts and most other non-volatile substances cannot come along; they stay in the chamber and gradually concentrate in the shrinking pool of water.
- Condense. The steam travels through a condensing coil — in Megahome units a 304 stainless-steel tube with aluminium fins — while a 15 W fan in the lid blows room air across the fins. The steam gives up its heat and turns back into liquid water.
- Polish and collect. The condensed water drips through a sachet of coconut-shell activated carbon in the spout and into a glass or PP collection bottle. The carbon captures volatile compounds that may have travelled with the steam and rounds off the taste.
When the chamber has boiled dry, its temperature rises quickly and a temperature-sensing switch cuts the power. The distiller stops on its own: you do not need a plug-in timer, and Megahome advises against using one.
What does distillation remove — and what can it miss?
The US Centers for Disease Control and Prevention (CDC) lists distillation among home treatments that remove parasites, bacteria and viruses, plus many chemicals, including arsenic, barium, cadmium, chromium, lead, nitrate, sodium, sulfate, calcium, magnesium and many organic chemicals. The University of Nebraska–Lincoln Extension adds fluoride, iron, manganese, chlorine and chloramines to the list, and describes distillation as removing up to 99.5 percent of impurities.
The weak spot is physics itself. A compound that boils at or below water's boiling point — some volatile organic compounds (VOCs) such as benzene and toluene, volatile solvents and certain pesticides — can vaporise along with the water and reach the condenser. The CDC notes that distillation does not remove some of these, and the University of Nebraska–Lincoln names an activated-carbon filter on the condensed water as one way to deal with them. That is the job of the post-filter.
| Stays in the boiling chamber | Can travel with the steam |
|---|---|
| Calcium and magnesium (hardness), sodium, sulfate, nitrate | Some volatile organic compounds, such as benzene and toluene |
| Lead, arsenic, cadmium, chromium and other metals | Some volatile solvents |
| Fluoride, iron, manganese | Certain pesticides |
| Bacteria, viruses and cysts | The items above are what the activated-carbon post-filter is there to reduce |
For a contaminant-by-contaminant look, read does a water distiller remove fluoride, lead and PFAS?
How is that different from a filter, or from boiling?
A filter works like a sieve or a sponge: water passes through a material, and only what that material can trap or adsorb is removed. Different filters target different things, and they need replacing on schedule to keep working. Distillation takes the opposite approach — instead of pulling impurities out of the water, it takes the water away from the impurities — so it deals with a wide range of dissolved substances at once, including the minerals most filters leave in.
Boiling a kettle is not the same either. Boiling kills microbes, but the water and everything dissolved in it stay together in the pot; as some water evaporates, salts and metals become slightly more concentrated. The US Environmental Protection Agency puts it plainly: boiling water does not remove lead. A distiller boils too, but it keeps the steam and leaves the residue. Our guides to distilled vs filtered water and boiling, filtering and distilling go deeper.
Why does a distiller take hours and use the electricity it does?
Turning water into steam takes far more energy than heating it. Warming a litre of water from room temperature to 100 °C needs roughly 0.09 kWh; boiling that litre away into steam needs about 0.63 kWh more. So even a perfect distiller needs around 0.7 kWh of heat for every litre it produces — that is physics, not inefficiency.
Megahome distillers are rated at 580 W (565 W for the heater and 15 W for the fan). Owners report that a 4-litre batch takes roughly 4.5–6 hours, so a typical batch uses about 0.58 kW × ~5.75 h ≈ 3.3 kWh, or roughly 0.8 kWh per litre — close to that physical floor. To see what this means at your local electricity price, multiply 0.8 by your price per kWh, or use our cost calculator.
The same physics explains two things owners notice. The heat taken out of the steam at the condenser has to go somewhere, so the fan blows it into the room, which warms slightly. And the fan is audible: one long-term owner review measured about 60 dBA, while a Japanese dealer lists 56 dB at 30 cm and 52 dB at 1 m. Many owners simply run their distiller in the kitchen or a utility room.
What is left in the chamber, and how do you keep it working well?
Everything the steam leaves behind stays in the boiling chamber. In hard-water areas that means a visible layer of white or brownish scale after each batch. Scale matters: the University of Nebraska–Lincoln notes that it reduces efficiency and raises electricity use, and owners report that baked-on scale is the most common reason the thermal reset switch trips early. Good habits are simple:
- Empty and rinse the chamber after batches, and pour the residue away — it is what the distiller removed, so do not drink or reuse it.
- Descale at least once a month with citric acid, as Megahome's instruction manual states, and more often if your water is hard.
- Replace the carbon sachet within 25 days, as the manual states, or sooner if the water tastes or smells unusual.
- Keep it clean between uses. The CDC notes that bacteria can grow on a distiller's cooling coils when it is not in use, and distilled water is pure, not sterile. After a few idle days, clean the unit and the bottle before you restart.
- Keep the fan and vents free of dust — the cooling airflow is part of how the distiller works.
With proper care, the University of Nebraska–Lincoln says a good distiller should last 10 to 15 years, and Megahome owners report many years of daily use.
Does the build of a distiller matter?
Because the steam path is the water path, the materials matter. Megahome has built countertop distillers in Tainan, Taiwan, since 1992, using a 304 stainless-steel boiling chamber as standard and 316 stainless steel in the MH-943SBS, with a stainless steam dome and a choice of glass or PP collection bottle. The MH943T-SW and MH943S-SW models hold TÜV Rheinland GS certificate 50514575, and as of September 2026 Megahome distillers have around 5,000 Amazon ratings averaging 4.5–4.7 stars. You can compare the MH-943TWS with the other models, or find a dealer near you on our where to buy page.
Key takeaways
- A distiller works in four stages: boil, evaporate, condense, then polish through activated carbon.
- Minerals, metals, salts and microbes stay in the boiling chamber; distillation removes the vast majority of impurities.
- Some volatile compounds can travel with the steam, which is why distillers use an activated-carbon post-filter.
- Turning water into steam needs about 0.7 kWh per litre in theory; a Megahome unit uses roughly 0.8 kWh per litre in practice.
- Descale at least monthly, replace the carbon sachet within 25 days, keep the unit clean — and no plug-in timer is needed.
Frequently asked questions
How long does a water distiller take to make 4 litres?
Owners of Megahome distillers report roughly 4.5–6 hours per 4-litre batch, depending on conditions such as the starting water temperature. The unit switches itself off when the chamber is empty.
Is water from a home distiller sterile?
No. Distillation removes the vast majority of impurities, but once the water reaches the collection bottle it is exposed to air and to the bottle and spout. Distilled water is pure, not sterile, so keep the bottle clean and covered. A home distiller is a household appliance, not a medical device or a steriliser.
Why does distilled water taste different?
Most of the taste of tap water comes from its dissolved minerals and from disinfectants such as chlorine. Distillation removes these, so the water tastes very neutral. Many owners describe it as crisp and clean; others find it flat at first and prefer it chilled.
Do I need to install a water distiller?
No. A countertop distiller needs no plumbing — just a power socket and a stable surface with space around the fan so the cooling air can flow freely.
Can I put anything other than water in it?
No. Use the distiller for water only. Megahome's warranty does not cover damage caused by liquids other than water.
Sources
- US CDC – About Home Water Treatment Systems
- University of Nebraska–Lincoln Extension – Drinking Water Treatment: Distillation (G1493)
- US EPA – Does boiling water remove lead?
- TÜV Rheinland Certipedia – GS certificate 50514575
- Nutriteam – Megahome water distiller product page
- CenturyLife.org – In-depth product review: Megahome countertop water distiller
- Megacat Japan – Megahome distiller product information
- Amazon.com – Megahome countertop water distiller (customer ratings)
