The same glass of water might be RO water, distilled water or mineral water. All three end up safe to drink; what differs is how they are treated, how they taste, how much mineral content they carry, and what they cost and take to manage over time. The conclusion first: for heavy everyday drinking with simple long-term management, plumbed-in RO filtration is what most offices and homes choose; distilled water wins on the simplicity and directness of its principle, but is slow to produce and heavy on electricity; mineral water's value lies in its minerals and taste, at the highest running cost of the three.
The difference between the three, in one table
| Item | RO water | Distilled water | Mineral water |
|---|---|---|---|
| Treatment method | Semi-permeable membrane filtration (0.0001 micron) | Boiled to vapour, then condensed | Natural source, filtered and bottled |
| Minerals | Mostly filtered out along with everything else | Almost entirely removed | Natural minerals retained |
| Taste | Clean, with little off-taste | On the flat side | Varies with the source |
| How it is supplied | Plumbed into the mains, made and drunk on the spot | Machine-made, or ordered in barrels | Bought by the bottle or by the case |
| Long-term cost structure | Cartridges and maintenance, on an annual basis | High electricity cost, or paid per barrel | Paid per bottle: the more you use, the more it costs |
RO water: plumbed-in filtration, made and drunk on the spot
RO (reverse osmosis) filters through a semi-permeable membrane with pores as fine as 0.0001 micron, which helps reduce bacteria, viruses, dissolved heavy metals and organic matter in the water. The quality of Hong Kong's mains water as it leaves the treatment works is regulated by the Water Supplies Department; problems mostly arise in building tanks and internal plumbing — and an RO system, installed at the point of use, deals with exactly that last stretch of the risk.
Two honest costs. First, the filtration process produces waste water; that is part of how RO works. Second, minerals are filtered out along with the impurities. The second matters little in practice — mineral intake comes mainly from food, and drinking water accounts for a small share of it — but anyone who minds about taste should note that RO water leans clean and light.
For offices and homes, RO's biggest advantage is really operational: plumbed into the mains, made and drunk on the spot, with no ordering, carrying or storing of water, and a long-term cost that comes down to budgetable cartridges and maintenance. Cartridges have set replacement cycles — pre-filters generally once a year, RO membranes generally every two to three years, subject to the maintenance arrangement.
Is distilled water pure water?
Close to it — but "pure" here is a physical description, not a measure of quality. Distillation boils water into vapour and condenses it again, leaving dissolved substances almost entirely behind, which is why laboratories and medical procedures use distilled water. In an everyday drinking context its drawbacks stand out instead: the process has to boil a whole tank, so its electricity use is the highest of these methods and it is slow to produce; minerals are removed just as completely, and the taste is generally reckoned flat.
Plenty of Hong Kong companies are in the habit of ordering barrelled distilled water, which is really a separate subject — what is being compared is not the water itself but the carrying, storage and administrative cost of the water-delivery model. For a detailed cost breakdown, seeHow water delivery pricing is calculated; for how a distilled water machine works and what maintaining one involves, seeWhat is a distilled water machine.
Mineral water: natural minerals, and the source decides everything
Mineral water is drawn from a natural source and keeps calcium, magnesium, sodium, potassium and other minerals; the taste varies with the source, which is precisely its selling point. Two things to watch: mineral content differs a great deal between brands, and how well the source is protected determines how consistent the water is; and it carries the highest running cost of the three — charged by the bottle, so on a busy site the spend rises out of all proportion. Most offices keep mineral water for hospitality and arrange something else for everyday drinking.
How should offices, schools and homes choose?
- Office: with a large headcount and heavy daily consumption, paying by the bottle or by the barrel does not work out over time, and a plumbed-in RO dispenser with scheduled maintenance is the mainstream approach. Smaller units of under ten people can start with a compact model.
- Schools: many draw-off points with peaks concentrated at recess and lunch, so the priorities are output and anti-scald design; a plumbed-in RO configuration is a common choice.
- Homes: an under-sink RO filter takes up no counter space, and cooking and drinking draw on the same supply; households that prefer the taste of natural minerals can run filtered water for everyday use alongside mineral water for guests.
Summary
None of the three is absolutely better than the others; there is only what suits. If you want long-term management to be simple and the cost controllable, choose plumbed-in RO. If you value the physical purity of near-zero dissolved solids and do not mind the electricity and the wait, distillation has its place. If you are willing to pay a higher running cost for natural minerals and taste, choose mineral water. To read further on how RO works and what to look for when buying, see the main articleWhat is RO water.
Related Bio-Link products
- RO838: an under-sink RO filter, suited to cooking and everyday drinking at home.
- DT400: a countertop instant-hot dispenser; a filtration system can be specified to suit the conditions on site.
- ST1523: an upright three-temperature RO dispenser with a 23-litre hot tank, suited to medium and large offices.
About Bio-Link
Bio-Link (霸力純水濾水系統) is one of Hong Kong and Macau's longest-established reverse-osmosis (RO) drinking-water specialists, operating since 1997 — nearly three decades focused almost entirely on RO. We supply, install and maintain direct-piped RO and UF drinking-water systems for homes, offices, schools, clinics, restaurants and hotels across Hong Kong and Macau, with one company handling supply, installation and maintenance end to end, to buy or to rent, with clear costs. Our full filtration line is SGS-tested and designated models meet NSF 42 & 58; Bio-Link is a certified Social Enterprise (HKCSS / SEE Mark SEE0195).
Frequently asked questions
Is distilled water pure water?
Distilled water has an extremely low dissolved-solids content and is physically the closest thing to "pure water", which is why laboratories and medical procedures use it. But what matters for everyday drinking is safety, taste and cost, and "pure" by itself does not make it better suited to drinking every day.
RO water has no minerals — is drinking it long term a problem?
Mineral intake comes mainly from food, and drinking water accounts for a small share of it. Distilled water contains no minerals either, so on this point there is little between them; the more useful comparison when choosing is cost structure and how each is managed.
Should an office use an RO dispenser or order barrelled water?
It comes down mainly to headcount and management cost. Barrelled water is charged by the barrel, so with more people and heavier use both the spend and the carrying burden rise; the cost of a plumbed-in RO dispenser is mostly cartridges and maintenance, billed annually and budgetable, and the advantage grows with headcount.
Further information: Beware of contamination in distilled water machines — CHOICE Magazine Issue 334 | Consumer Council