Reverse Osmosis: How it Works and Why It's the Best Drinking Water Protection Today | CzystyStyl Guide

Is tap water in Poland safe?

Water supplied by Polish waterworks undergoes regular checks and must meet stringent quality standards defined by national and EU regulations. This means that upon leaving the treatment plant – for example, Warsaw's MPWiK, which uses ozonation, active carbon filtration, and performs tens of thousands of laboratory tests annually – the water is truly safe for consumption.

The problem is that before it reaches your glass, it still has to flow through the water supply network and the building's internal installation. In older buildings – tenements, blocks from the communist era – there are still sections of installations made of galvanized steel prone to corrosion, and in some places even lead connections or asbestos-cement pipes. It is precisely on this "last meter" that certified water can lose its quality, acquire a metallic taste or smell.

The European Union has therefore tightened the Water Directive (2020/2184) – it has lowered the permissible lead concentration and, for the first time, introduced limits for PFAS, i.e., "forever chemicals". However, replacing all old installations in Poland is a process that will take decades, so responsibility for water quality on the last section practically rests with apartment owners. Therefore, many people decide to use additional filtration directly at the point of water consumption.

What is reverse osmosis?

To understand how RO filters work, it's worth first explaining what osmosis itself is.

Osmosis is a natural process occurring in nature – among others, in living cells. It involves the spontaneous flow of water molecules through a semipermeable membrane, from a solution with a lower concentration of dissolved substances to a solution with a higher concentration, without the supply of additional energy.

Reverse osmosis uses the same principle but reverses the direction of flow using pressure. Water is pushed through a special semipermeable membrane that allows almost exclusively water molecules to pass through, retaining most of the dissolved impurities. Hence the name of the technology – Reverse Osmosis (RO).

The membrane pores are about 0.0001 micron in size – about 10,000 times smaller than a typical microplastic particle, and bacteria and viruses are hundreds, even thousands of times larger. Therefore, the RO membrane acts as a physical barrier through which virtually nothing but water can pass.

How does a reverse osmosis filter work?

Although modern reverse osmosis systems consist of several filtration elements, their operating principle is simple. Water from the municipal water supply successively passes through a mechanical filter, an activated carbon filter, a reverse osmosis membrane, and finally – depending on the model – through a post-filter or a mineralizer, before reaching a dedicated tap at the sink.

Each of these stages is responsible for removing a specific group of contaminants and protecting subsequent system elements from damage. The final result is water of very high purity and good taste, available directly from the tap – without boiling, pouring, or waiting for a jug.

What does a good reverse osmosis filter consist of?

Although the RO membrane is the most important element of the entire system, it alone would not ensure effective and long-lasting operation. Therefore, a good RO filter usually consists of several cooperating filtration stages:

1. Mechanical filter – most often made of polypropylene non-woven fabric, it retains sand, rust, and sludge that could damage subsequent cartridges.
2. Activated carbon filter – removes chlorine, organic compounds, and substances affecting the taste and odor of water, while protecting the membrane from degradation due to chlorine.
3. Reverse osmosis membrane – the heart of the system, with pores around 0.0001 micron in size, retaining most dissolved impurities.
4. Post-filter or mineralizer – improves water taste or enriches it with selected minerals, primarily calcium and magnesium.
5. Additional elements – modern systems also feature pressure-boosting pumps, UV lamps, or smart cartridge replacement sensors.

Regular replacement of preliminary cartridges every 3–6 months is essential – neglected preliminary filtration is the most common cause of premature wear of the expensive membrane.

What impurities does reverse osmosis remove?

The biggest advantage of reverse osmosis is its extremely wide range of filtration. Unlike simple carbon filters or filter jugs, an RO membrane removes not only substances affecting the taste and odor of water, but also many dissolved impurities invisible to the naked eye.

Modern membranes remove up to 99% of typical impurities present in drinking water, including, among others:

• heavy metals (e.g., lead, cadmium, mercury, and arsenic),
• bacteria and viruses,
• microplastics and a significant portion of nanoplastics,
• pesticides and herbicides,
• most PFAS compounds,
• nitrates and nitrites,
• excess mineral salts responsible for high water hardness,
• many other organic and inorganic pollutants.

Thanks to such high effectiveness, this technology is used not only in homes but also in laboratories, medicine, and the food industry.

Is water from reverse osmosis healthy?

This is a question almost every customer asks before deciding to buy. One of the most common myths is the belief that water from reverse osmosis is "dead" or unsuitable for daily drinking. Current scientific knowledge does not support such claims.

The primary function of water in the body is hydration, not providing minerals – this role is primarily fulfilled by a balanced diet. Even in regions with hard water, the calcium content is usually 60–120 mg/l (in Warsaw it's about 90–108 mg/l), and in exceptionally hard water, it can exceed 150–200 mg/l. Meanwhile, the daily calcium requirement for an adult is about 1000 mg. To cover this solely with water, one would have to drink 5 to even 15 liters daily – which is practically unrealistic.

There is also no basis to fear "flushing out" minerals from the body. Healthy kidneys and the hormonal system continuously regulate electrolyte balance regardless of how many minerals the consumed water contains – they simply adjust the amount of urine excreted.

This does not mean that the presence of minerals in water is undesirable – many people simply prefer water with a more natural, "spring-like" taste. This is why manufacturers of modern systems increasingly equip them with mineralizers or allow for their later installation.

Remineralization – is it needed?

The RO membrane very effectively removes dissolved mineral salts, so purified water has a low mineralization level. For some, this doesn't matter; others prefer water with a fuller taste and slightly higher content of selected minerals.

That's why many modern RO systems have a mineralizer built-in at the factory or allow for easy installation later. Water flowing through such a cartridge is enriched primarily with calcium and magnesium ions, giving it a milder taste and, depending on the medium, a slightly higher pH.

However, a mineralizer is not always necessary. People who prepare coffee using alternative methods, brew high-quality teas, or use devices requiring water with very low mineralization often choose water without additional remineralization. Most households, however, prefer a taste similar to good spring water – and in such a case, a mineralizer is a simple way to achieve it.

After the mineralizer, ionizing or structuring cartridges can be additionally connected to the system. Manufacturers attribute improved taste and "structure" to the water, although these effects are not unequivocally scientifically confirmed – if you still want to try them, you can find them in our collection of structuring cartridges.

Classic system or Direct Flow?

Just a dozen years ago, the vast majority of household RO systems used a tank to store purified water. This was due to the limited efficiency of membranes at the time, which produced water more slowly than the current demand of household members – a standard membrane yields only a few to a dozen liters of permeate per hour, so without a tank, one would have to wait several minutes to fill a glass.

Modern membranes with capacities of 400, 600, 800, and even 1200 GPD have enabled the development of Direct Flow systems – tankless systems that, thanks to a built-in pressure-boosting pump, produce purified water on demand, as soon as the tap is opened. Their additional advantage is their compact design (a housing only a dozen centimeters thick), which allows them to fit even in small kitchen cabinets.

Both solutions have their place – classic systems are usually cheaper to start with, while Direct Flow offers convenience, space-saving, and lower water consumption. Interestingly, it is in classic systems that mineralizing and structuring cartridges usually work somewhat more effectively – due to the lower permeate production efficiency, water flows through the mineral bed more slowly, giving it more time to contact minerals and become better saturated. In the CzystyStyl offer, you will find both types from renowned manufacturers: Philips, Ecosoft, ViO, Midea, Supreme, and Bluewater.

Examples of high-production Direct Flow filters:

• Klarwod RO-UX6-800G
• SUPREME CLEVER 1200 GPD
• VIO AW-RB36 1000 T

How to maintain system hygiene?

The membrane itself is impermeable to bacteria, but in classic systems with a tank, the environment after the membrane – i.e., the tank itself – requires regular disinfection, recommended approximately once a year. Direct Flow systems, due to the lack of a tank and continuous water flow, practically eliminate this risk, which for many customers is an additional argument for choosing this type of solution.

Does reverse osmosis use a lot of water?

This is one of the most frequently asked questions about RO filters. It is a fact that some water during filtration goes down the drain along with retained impurities – this is a natural part of every RO membrane's operation, preventing scale buildup on its surface.

However, modern devices are now much more efficient than older designs. In the best Direct Flow systems, the ratio of pure water to wastewater is as high as 2:1 (for every 2 liters of pure water, only 1 liter goes down the drain), while older classic models typically achieved 1:4 or 1:5. The actual result depends on the specific model, pressure in the installation, and the quality of the inlet water – parameters provided by manufacturers refer to specific test conditions.

Examples of filters with the best water rejection rate (for every 2 liters of pure water – only 1 liter to drain):

• PHILIPS AUT8940
• Midea 600GPD RO5 with WiFi
• Klarwod RO DIGITAL 600G

Summary

Reverse osmosis has remained one of the most effective methods of home water filtration for years. Thanks to its semi-permeable membrane, it removes up to 99% of typical impurities present in drinking water, improving its taste, smell, and safety.

Modern RO systems differ significantly from those of a dozen years ago – higher membrane efficiency, compact design, quick cartridge replacement, and optional mineralization make it a convenient solution for both apartments and single-family homes today.

However, the choice of a specific system should always be tailored to individual needs, water quality, and the number of household members – there is no single ideal device for every situation.

Check out the reverse osmosis systems available at CzystyStyl

Our offer includes both classic RO systems with a tank and modern Direct Flow devices from renowned manufacturers: Philips, Ecosoft, ViO, Midea, Supreme, and Bluewater. We offer only proven solutions, original filter cartridges, and professional advice before and after purchase.

➡ See all reverse osmosis filters