Filtration, purification, softening, reverse osmosis: what is the difference?

These terms are often confused, even though they do not address the same issue. The right system depends first on what you wish to improve: limescale, taste, odours, certain pollutants, or the quality of drinking water.

The answer in brief

• Water softening combats limescale and protects the entire house.
• Filtration targets certain elements: sediments, chlorine, odours, taste, or contaminants depending on the medium used.
• Purification is a general term: it refers to water from which certain undesirable substances have been reduced through one or more technologies.
• Reverse osmosis is an advanced purification solution, primarily used for drinking water, which reduces many dissolved elements.

The best system is not necessarily the one that filters the "most": it is the one that precisely addresses your problem, at the point where you need it.

Filtration: improving targeted water

Filtration is a broad term. It encompasses several technologies capable of reducing certain particles and substances present in water, depending on the type of cartridge or medium used.

For example, a sediment pre-filter can capture sand, rust, or suspended particles. An activated carbon filter is often chosen to reduce the taste and odour of chlorine as well as certain organic compounds.

Filtration is particularly suitable if you notice:

• A taste or smell of chlorine.
• Visibly cloudy water or water loaded with particles.
• Rust or sediment deposits.
• The desire to improve drinking water without installing a very comprehensive system.
• A pre-filtration designed to protect another piece of equipment.

To remember : a filter is not automatically a water softener. 
A standard filtration generally does not sufficiently reduce calcium and magnesium to stop limescale.

Softening: the solution against limescale

A water softener primarily treats water hardness, that is to say, the minerals responsible for limescale: mainly calcium and magnesium. The goal is to limit deposits, white marks, and scaling of installations.

It is a relevant solution to protect equipment that uses hot water: boiler, heating system, washing machine, dishwasher, taps, shower, coffee machines, or pipes. It can also improve daily comfort, for example, when soap does not lather well or when laundry feels rough.

Softening should be prioritised if you observe :

• White marks on glasses, shower walls, or taps.
• A kettle or coffee machine that scales quickly.
• Devices that consume more or break down faster due to limescale.
• A feeling of rough skin or hair after showering.
• Stiff laundry and a high consumption of household products.

Important : a water softener does not replace a filter dedicated to drinking water. 
It is not designed to reduce chlorine, PFAS, lead, nitrates or other targeted contaminants.

Purification: a goal

The word purification mainly describes the desired outcome: obtaining water free, in whole or in part, from undesirable elements. 
The method can combine mechanical filtration, activated carbon, membrane, UV disinfection or other processes depending on the water analysis and intended use.

Therefore, “purified” water does not always mean the same thing. 
A system can be excellent for improving taste and odour, without necessarily being intended to reduce dissolved salts, nitrates or certain metals.

To choose correctly, ask yourself two questions:

1. What is the observed problem? Limescale, odour, chlorine, particles, taste, identified contamination?
2. Where does treatment need to occur? The whole house, just the shower, or only the drinking water in the kitchen?
   
   

Reverse osmosis: a very advanced filtration

Reverse osmosis uses a semi-permeable membrane. 
Under pressure, water passes through this membrane while a large part of the dissolved substances is retained or expelled with the reject water.

It is particularly suitable when looking for drinking water that is very low in dissolved substances: salts, nitrates, fluorides, certain heavy metals and several contaminants that are difficult to reduce with simple filtration.

Reverse osmosis can be a good choice if you wish to:

• Significantly reduce dissolved substances in drinking water.
• Target nitrates, fluorides or certain metals such as lead or arsenic.
• Have water suitable for drinking, tea, coffee and cooking.
• Reduce certain PFAS, subject to the performance and certifications indicated by the manufacturer.
• Install a dedicated solution under the sink or on the worktop.

Reverse osmosis is not necessarily designed to replace a softener for the entire installation. It is generally used at the point of use, most often in the kitchen, while the softener protects the household equipment from limescale.

What solution for which problem?

Can the solutions be combined?

Yes, and it is often the most coherent approach. A central system can treat limescale to protect the installations, while a dedicated filter or a reverse osmosis unit installed under the sink treats the water used for drinking and cooking.

Example: a family living in a very limescale-prone area can install a water softener to preserve the boiler, sanitary facilities, and appliances, then add a filtration or reverse osmosis solution in the kitchen to improve drinking water.

Before choosing: analyse the water

A reliable decision starts with identifying the problem.
Hardness, the presence of particles, taste, smell, and the results of an analysis do not lead to the same solutions.

At Mizuro, the right starting point is therefore simple: assess your water, your consumption habits, and your equipment before proposing a system.
This avoids oversizing the installation or installing a solution that does not meet the actual need.