You want to filter the water in your home, but a single search is enough to be faced with a dozen solutions: carafe, under-sink filter, activated carbon, reverse osmosis, water softener, filter installed on the main water supply… It is difficult to know what really meets your needs.

To choose a water filter for the entire house, you must start by distinguishing two things: what you wish to reduce in your water and which water points you want to treat. Because the best system is not necessarily the one that filters the most finely. It is the one that treats the right parameters, with a flow rate and operation adapted to your home.

Filtering a tap or the entire house: what's the difference?

The first question to ask yourself concerns where the system is installed. A distinction is generally made between point-of-use filtration and point-of-entry filtration.

A point-of-use system treats water at a specific location. This is the principle of a filter attached to the tap, an under-sink device, or many domestic reverse osmosis systems. Kitchen water can thus be treated for drinking and food preparation, while water for the shower, bathroom, or other taps does not pass through the system.

Point-of-entry filtration works differently. The device is installed on the main water supply, before water is distributed throughout the home. The U.S. Environmental Protection Agency uses the term "Point-of-Entry" to designate these systems capable of treating the water supply of a building for most or all of its uses.

It is therefore this type of installation you should look at if your goal is really to filter the water for the whole house. The water is treated once, upstream, then distributed to the various water points.

The benefit is then no longer limited to the glass you drink. Depending on the chosen technology, filtration can also concern water used for cooking, washing, or supplying certain household equipment.

Which systems allow you to filter water at home?

The available solutions are not interchangeable. A filter carafe, a water softener, and a reverse osmosis membrane do not have the same objective, location, or constraints.

System	Treated area	Main role	Points to consider
Carafe or tap filter	One point of use	Taste, odors, and certain compounds depending on the cartridge	Small volume, frequent consumables
Under-sink filter	One tap	Depends on the filter media used	Does not treat other water points
Centralized activated carbon	Whole house	Chlorine, tastes, odors, and certain organic compounds	Does not address all contaminants
Reverse osmosis	Often one point of use	Advanced membrane filtration	Water waste, flow rate, and minerals to consider
Water softener	Whole house	Reduction of water hardness	Not a contaminant filter
Multi-stage centralized filtration	Whole house	Variable depending on the technologies involved	Must be sized to the home's flow rate

This table highlights an essential point: there is no single technology capable of responding to all issues in the same way. Before buying a device, you must therefore know why you want to filter your water.

If your main annoyance concerns taste or odor, activated carbon can already provide an adapted answer. It works by adsorption: certain substances attach themselves to the surface of the carbon as water flows through it.

If your problem is primarily limescale, you should look into water softening instead. A water softener acts on the ions responsible for hardness, notably calcium and magnesium, generally thanks to an ion-exchange resin. Its main objective is to limit the scaling of equipment and pipes. It should therefore not be presented as the equivalent of a system designed to reduce contaminants.

Reverse osmosis follows a different logic. Pressure forces water through a semi-permeable membrane, which allows many dissolved substances to be retained. The World Health Organization classifies reverse osmosis among the membrane processes used for the treatment of drinking water.

However, this technology produces two streams: treated water and a concentrate containing the retained substances. The latter is discharged. The EPA notes that conventional point-of-use domestic reverse osmosis systems can reject several volumes of water for every volume of treated water, although the latest, most efficient devices significantly improve this ratio.

To better understand the differences between membrane processes, our article on nanofiltration and its differences with reverse osmosis details how they work.

How to choose the best water filter for the whole house?

Rather than only comparing the number of filtration stages or the fineness announced by manufacturers, start with your water. It is what should determine the system.

If your home is supplied by the public network, you can check the results of your municipality's health inspections. A complementary analysis may also be relevant when you are looking for a particular parameter or when your internal installation is likely to have an influence on the tap water.

Taste and odor provide some indications, but they do not allow you to know the composition of the water. Substances can be present without being perceptible. Conversely, water whose taste you dislike is not necessarily unfit for consumption.

Our article dedicated to contaminants present in network water in France helps identify the main families of monitored substances and their origin.

Once your objective is defined, four criteria are particularly important:

• the contaminants or parameters that the technology is actually capable of reducing;
• the flow rate required to supply several water points simultaneously;
• the pressure required to operate the system;
• the frequency and cost of replacing consumables.

Flow rate is particularly important for a centralized installation. An under-sink filter generally supplies a single tap. On the main supply, it must be able to keep up with the house's consumption when several uses occur simultaneously: one person taking a shower while another uses a tap, for example.

A system that is too restrictive can lead to a drop in pressure or an uncomfortable flow rate. Conversely, unnecessarily oversizing the installation can increase its cost and footprint without real benefit.

Centralized or under-sink filtration: which to choose?

The choice mainly depends on what you want to filter. If your only concern is water for drinking and cooking, an under-sink system may be sufficient. It treats a limited volume and concentrates the filtration on the use you are interested in.

This approach can also allow the use of a technology that would be more restrictive to apply to the entire home. This is precisely why many domestic reverse osmosis systems are installed under the kitchen sink.

Conversely, centralized filtration makes full sense when you want water to be treated before it is distributed throughout the house. You then do not need to install a filter on every tap.

This distinction is important when comparing prices. A 100 or 200 euro device installed on a single tap does not meet the same need as equipment placed on the main water supply. Comparing only their purchase price therefore amounts to comparing two different services.

You must also look at maintenance over several years. The price of cartridges, their replacement frequency, potential electrical requirements, and the process's water consumption can eventually weigh more heavily than the initial price difference.

Finally, centralized filtration does not necessarily imply electrical consumption. Some systems use the pressure already available in the domestic network to circulate water through the filter elements. We explain this principle in more detail in our guide to filtering water without electricity at home.

Softener, reverse osmosis, or centralized filter: beware of confusion

One of the most frequent mistakes is choosing a known device rather than a device adapted to the problem encountered.

Do you have many white marks on the shower wall and your kettle scales up quickly? You are probably dealing with hard water. A softener might be relevant. But reducing water hardness and reducing contaminants are two different objectives.

Do you want to obtain very low-mineral water only for drinking and cooking? Reverse osmosis can meet this need, with the constraints specific to this technology: pressure, flow, maintenance, and the production of a reject stream. The EPA clearly distinguishes point-of-use reverse osmosis systems, connected to a single water point, from point-of-entry systems intended to treat the entire building.

Are you instead looking to act on several families of contaminants while maintaining normal water use throughout the house? Centralized filtration combining several technologies may be more consistent.

The right question is therefore not "which technology filters the most?", but "which technology matches my water and my uses?" Extremely advanced filtration does not necessarily provide additional benefit if it treats parameters that are not problematic for you, while adding constraints you do not need.

This logic also applies to certifications and test results. When comparing equipment, verify precisely what has been tested: technology involved, substances analyzed, test conditions, and measured performance. A general statement like "filters 99% of pollutants" is much less informative than a result associated with identified contaminants and a precise protocol.

What solution to filter all the water in a house on a daily basis?

For an individual who wishes to treat the water for their entire home, an installation on the main supply has an obvious advantage: it centralizes the filtration. A single installation intervenes before the water is distributed to the various points of use.

This is the principle of the FLX Compact. It is installed on the home's water supply and uses the network pressure to circulate water through its filtration system. It thus operates without electricity or the addition of chemical products.

Its filtration combines several mechanisms intended to reduce the contaminants targeted by the system, as well as bad tastes and odors. The objective is to treat the water in a centralized manner rather than equipping each tap separately.

This operation does not, however, mean that the FLX Compact is automatically the best choice for every home. If your problem is exclusively limescale, a specific hardness treatment may be more suitable. If you only wish to filter a few liters for drinking, a point-of-use device may suffice.

On the other hand, if your goal is indeed to filter water before it is distributed throughout the house, the point-of-entry is the logical location to prioritize. It then remains to compare technologies according to your water, the necessary flow rate, their maintenance, and documented performance on the contaminants that concern you.

Frequently asked questions

Where to install a filter to treat all the water in the house?
A centralized system is installed on the main water supply, before distribution to the various water points in the home. The exact location depends on the configuration of the installation and the manufacturer's recommendations.

Does a softener filter the water in the house?
A softener mainly treats water hardness by acting on calcium and magnesium. It therefore does not fulfill the same role as a system intended to reduce different families of contaminants.

Should you choose a reverse osmosis system to filter the whole house?
Not necessarily. Reverse osmosis allows for very advanced filtration, but domestic units are often installed at the point of use. Treating the entire house by reverse osmosis involves other constraints regarding flow, sizing, and water waste.

Can you filter the whole house without electricity?
Yes. Some systems use the network pressure directly to circulate water through the filter elements and therefore do not require an electric pump.

How do I know which filter corresponds to my water?
Start by identifying the parameters you wish to treat using your municipality's water quality data or, if necessary, an analysis. You will then be able to check which technologies have documented performance on these parameters.

The best system for filtering the water for the whole house is ultimately not the one that promises to do everything. It is the one that matches the quality of your water, your uses, and the flow rate your household actually needs. Before comparing devices, start with your objective: treating limescale, improving taste, reducing certain contaminants, or filtering water in a centralized way. Choosing the technology then becomes much simpler.

Sources

• World Health Organization – Guidelines for Drinking-water Quality, membrane treatment processes: https://www.who.int/docs/default-source/wash-documents/wash-chemicals/treatment-methods-and-performance.pdf
• U.S. Environmental Protection Agency – Point-of-Use or Point-of-Entry Treatment Options for Small Drinking Water Systems: https://www.epa.gov/sites/default/files/2015-04/documents/epa815r06010.pdf
• U.S. Environmental Protection Agency, WaterSense – Point-of-Use Reverse Osmosis Systems, specification and operation: https://www.epa.gov/watersense/point-use-reverse-osmosis-systems
• Ministry of Health – Quality of water intended for human consumption: https://sante.gouv.fr/sante-et-environnement/eaux/eau