"Water purifier" is today a name applied to very different things: a €25 pitcher, a reverse osmosis system installed under the sink, and a €1,000 countertop appliance with hot and cold water. All "purify." None do the same thing.
This guide helps you choose wisely: how each technology works, what each actually removes, how much it costs to maintain after a year, and eight points to check before paying.
The five solutions, side by side
| Type | Technology | Removes | Installation | Investment |
|---|---|---|---|---|
| Filter pitcher | Activated carbon + resin | Chlorine, taste, odor, some metals | None | €20–40 |
| Tap filter | Activated carbon | Chlorine and sediments | Screw onto tap | €25–60 |
| Ultrafiltration (UF) | Membrane ≈ 0.01 µm | Bacteria, particles, turbidity, chlorine | Countertop or under sink | €100–400 |
| Under-sink reverse osmosis | RO membrane ≈ 0.0001 µm | Dissolved salts, limescale, chlorine, heavy metals | Plumbing work + extra tap + drainage | €150–500 + assembly |
| Countertop purifier with RO | RO membrane + hot/cold water | Same as above | None — place and plug in | €400–1,200 |
How reverse osmosis works
Reverse osmosis (RO) forces water, under pressure, through a semi-permeable membrane with pores on the order of 0.0001 microns. To put it in perspective: a bacterium measures about 1 micron, meaning it is ten thousand times larger than the pore. Virtually only water molecules pass through.
A typical system has four stages:
- Sediment pre-filter — retains sand, rust, and particles that would damage the membrane.
- Activated carbon — removes chlorine. Mandatory stage: chlorine degrades the RO membrane.
- Reverse osmosis membrane — this is where dissolved salts, limescale, nitrates, and heavy metals are removed.
- Carbon post-filter — refines the taste before the water comes out.
TDS: the number that shows the difference
TDS stands for Total Dissolved Solids — in ppm. It's the fastest way to see if a purifier is doing what it promises, and it's measured with a pocket meter that costs a few euros.
Tap water in a hard water area can show values of several hundred ppm. After reverse osmosis, it commonly drops to a fraction of that value. A filter pitcher, by comparison, hardly affects the TDS: it improves the chlorine taste, but the dissolved salts remain.
Honest note: a lower TDS is not synonymous with "healthier water." It is an indicator of how much dissolved material has been removed — nothing more. It serves to compare technologies, not to judge potability.
Rejected water
Every reverse osmosis system produces rejected water: part of the water is used to flush away what was retained in the membrane. In systems connected to the plumbing, this water goes down the drain. In countertop appliances, it is collected in a separate tank that is emptied periodically — which is why these devices work without any connection to the sewage system.
Anyone who tells you that a reverse osmosis purifier does not generate rejected water is not being accurate.
Ultrafiltration or reverse osmosis?
This is the most critical technical decision, and it depends on the water you have at home.
- Ultrafiltration retains particles, turbidity, bacteria, and cysts, and maintains dissolved salts. Filters are generally cheaper, with no rejected water, and no electricity for filtration. But it does not reduce hardness: if limescale is your problem, UF will not solve it.
- Reverse osmosis acts on the dissolved fraction — limescale, nitrates, heavy metals — it is the only one that truly alters the taste of hard water, but it produces rejected water and has more expensive filters.
How to decide in 10 seconds: do you live in the North, with soft water, and only chlorine bothers you? UF or even a filter pitcher will suffice. Do you live in Lisbon, Alentejo, or Algarve, with hard water, and don't like the taste or want limescale in your kettle? Reverse osmosis.
If you don't know which case applies to you, first read our article on the quality and hardness of tap water in Portugal.
With installation or countertop?
Technically, a good countertop reverse osmosis purifier performs the same treatment as an under-sink system. The difference lies in the logistics — and it's a difference that for many people decides everything.
| Under-sink | Countertop | |
|---|---|---|
| Work | Drilling, connection to mains and drain, additional tap | None — place and plug in |
| Rented home | Usually requires landlord's permission | No permission required |
| Moving house | Dismantle and reinstall | Carried by hand |
| Hot/cold water | Usually not | Yes, at chosen temperature |
| Space | Occupies lower cabinet | Occupies countertop |
| Autonomy | Continuous | Depends on the tank — needs refilling |
In Portugal, where a significant portion of families live in rented accommodation and apartment kitchens rarely have space under the sink, the countertop version solves a real problem — and is the reason why the demand for "installation-free water purifiers" has been growing consistently.
Eight points to check before buying
- CE marking and declaration of conformity. Mandatory for commercialization in the European Union. A serious seller provides them without hesitation.
- Warranty. In Portugal, Decree-Law no. 84/2021 establishes a 3-year legal warranty for movable goods sold to consumers. Be suspicious of anyone who advertises only 1 year — that is the factory export standard, not what Portuguese law requires.
- Price and availability of filters. This is where you pay in the long run. Ask how much each filter costs, how often it needs to be replaced, and if stock will still be available three years from now. A cheap appliance with expensive filters is a bad deal.
- Tool-free replacement. Quick-connect filters avoid relying on technical assistance for a two-minute operation.
- Tank capacity. Both for clean water and rejected water. Determines how often you will need to return to it.
- Noise. Models with a compressor (cooling or ice) make noise occasionally, like a small refrigerator. In an open-plan kitchen, this matters.
- Panel and manual language. This seems like a minor detail until you receive a device with the panel in Chinese characters. Confirm beforehand.
- Delivery time and customer support. If something goes wrong, you want to speak to someone who responds in Portuguese and within the same legal framework.
How much a purifier costs in Portugal
Market price ranges, for reference:
- €20–60 — filter pitchers and tap filters. Solve chlorine and taste issues.
- €150–400 — under-sink reverse osmosis systems, excluding installation (which usually adds €80–150).
- €400–900 — countertop purifiers with reverse osmosis and hot/cold water.
- €900–1,500 — top-of-the-range, with additional functions such as UVC sterilization or ice production.
A useful warning: in the Portuguese market, countertop devices advertised above €1,400 often differ from €800–900 models mainly in marketing, not in the membrane. Before paying double, compare the technical specifications line by line — filtration stages, capacity, power, filter cost — and ask what justifies the difference.
The UMBOX range
We selected three countertop reverse osmosis models, for three different uses. All work without any installation: just place them, fill the tank, and plug them in.
| Model | For whom | Highlight | Price |
|---|---|---|---|
| UMBOX W16 | Couples and small homes | Reverse osmosis + instant hot water | €549.00 |
| UMBOX W19 | Families — the most balanced | Reverse osmosis, hot and cold water, 8 L tank, UVC sterilization | €899.00 |
| UMBOX W91 | For those who entertain at home | Reverse osmosis, hot and cold water, ice production in 8–15 minutes | €1,049.00 |
Common conditions across the range:
- Free shipping to mainland Portugal
- 3-year warranty, in accordance with Decree-Law no. 84/2021
- Product by order — dispatch in 10 to 20 working days after payment confirmation
- Customer support in Portuguese
View the complete range of UMBOX water purifiers
Frequently asked questions
What is the difference between a water purifier and a water filter?
In commercial practice, the terms are often mixed. "Filter" has conventionally referred to solutions that retain particles and chlorine (pitchers, tap filters), while "purifier" refers to multi-stage systems that also act on the dissolved fraction — typically through reverse osmosis or ultrafiltration. What matters is not the name on the advertisement, but the technology inside.
Does a countertop purifier need a connection to the plumbing?
No. The clean water tank is filled manually, and the rejected water tank is emptied periodically. Only an electrical outlet is needed.
How often are the filters changed?
It depends on the model, the quality of the source water, and consumption. Sediment and carbon pre-filters usually last 6 to 12 months; the reverse osmosis membrane lasts considerably longer. In hard water, the intervals shorten. Always consult the manufacturer's instructions in the product data sheet.
How much electricity does it consume?
The filtration itself consumes little. What impacts the bill are the heating and cooling functions, which only activate when requested. Models with ice production, having a compressor, consume more than the others.
Is it worth buying a purifier if the water in my area is soft?
If the water is soft and the only nuisance is chlorine, a filter pitcher solves the problem for much less money. A reverse osmosis purifier is mainly justified for hard water, or when you also seek the convenience of having hot and cold water ready at any time without boiling or chilling.
What warranty do I have when buying in Portugal?
Three years of legal conformity warranty, under Decree-Law no. 84/2021, applicable to movable goods sold to consumers. In addition, there is the right of free resolution within 14 days for distance purchases, under Decree-Law no. 24/2014.
In summary
There is no "best purifier." There is the one suitable for your type of water, your kitchen, and your budget:
- Soft water, only chlorine is bothersome → filter pitcher.
- Hard water and possibility of plumbing work → under-sink reverse osmosis.
- Hard water, rented home or no space, and desire for hot and cold water at all times → countertop purifier with reverse osmosis.
Before deciding, calculate what you already spend today: how much bottled water costs a Portuguese family per year.
Prices and specifications valid at the time of publication and subject to change. Consult each product's data sheet for updated information.