Reverse osmosis system: for or against?

For: reverse osmosis can significantly reduce mineral content and many dissolved contaminants, improve certain water characteristics, and eliminate the need to buy bottled water regularly.

Against: an RO system requires regular maintenance, produces wastewater, may require electricity depending on the model, and also reduces dissolved minerals.

The right choice therefore depends primarily on your water, how you use it, and your priorities.

The advantages of an RO system

The main benefit of an RO system is its ability to produce water with very low levels of many dissolved substances.

1. Significant reduction of many dissolved substances

Reverse osmosis uses a semipermeable membrane that can significantly reduce the concentration of many dissolved salts and certain contaminants.

However, exact performance depends on the membrane, pressure, incoming water quality, and system maintenance.

To understand the process: what is reverse osmosis?

2. Reduction of TDS and mineral content

An RO system significantly reduces TDS, which is the total amount of measurable dissolved substances in water.

This can be desirable when you want water with a low mineral content.

Learn more: what is TDS?

3. Possible improvement in taste and certain water characteristics

The pre-filtration stages, particularly activated carbon, can help reduce certain substances responsible for unwanted tastes or odors.

However, the result depends on the water's initial composition and the system used.

4. A practical solution for some households

Once installed, an RO system lets you produce water directly at home without regularly having to carry bottles.

This benefit is particularly useful for households that consume a lot of bottled water.

5. Several configurations available

RO systems are now available:

• with a tank;
• with direct flow;
• with a booster pump;
• with low wastewater production;
• with remineralization;
• in compact or high-flow models.

You can therefore match the system to the available space, your household's consumption, and the pressure in your plumbing system.

The disadvantages of an RO system

An RO system is not a perfect solution, and certain drawbacks need to be considered before you buy.

1. It produces wastewater

Reverse osmosis works with two flows: some of the water passes through the membrane, while another portion carries away some of the retained substances.

The volume of wastewater varies considerably depending on the model, pressure, membrane, and operating conditions.

It is therefore better to compare the actual water efficiency of the units than to assume that the same ratio applies to all RO systems.

2. It requires regular maintenance

The pre-filters, membrane, and any post-filters must be replaced periodically.

Poor maintenance can reduce system performance.

3. It also reduces dissolved minerals

Reverse osmosis does not selectively remove only the substances you want to eliminate: it also reduces the concentration of many minerals naturally present in water.

Some users therefore choose to add a remineralization filter cartridge after the membrane.

See: remineralization solutions .

4. Some models require electricity

Many direct-flow or high-flow RO systems use a pump. They therefore require an electrical supply near the installation.

5. The installation takes up space

An under-sink system requires space for the unit, filters, and possibly a tank.

You also need to leave enough space to perform maintenance.

6. The purchase price is not the total cost

In addition to the initial price, you need to factor in:

• pre-filters;
• the membrane;
• any post-filters;
• any remineralization;
• water consumption associated with wastewater;
• possibly electricity.

RO system: summary of the main pros and cons

When can an RO system be a suitable choice?

An RO system can be particularly useful if:

• you want to significantly reduce the concentration of dissolved substances;
• your goal is to obtain water with a low mineral content;
• you currently consume a lot of bottled water;
• you want to produce your filtered water directly at home;
• you have identified a treatment need that is compatible with reverse osmosis;
• you are willing to maintain your unit regularly.

When might an RO system not be the best choice?

An RO system is not automatically necessary in every situation.

Another technology may be more suitable if:

• your only goal is to reduce the taste or smell of chlorine;
• you want to retain most dissolved minerals;
• you do not want any wastewater;
• you do not want to perform periodic maintenance;
• your under-sink space is very limited and no other configuration is possible.

In these situations, an activated carbon filter, ultrafiltration, or another technology may sometimes be more suitable.

How much wastewater does an RO system produce?

There is no single ratio that applies to all RO systems.

The amount of wastewater depends in particular on:

• the membrane;
• the inlet pressure;
• the water temperature;
• the control system;
• whether a pump is present;
• the overall design of the unit.

When comparing two models, always check whether the manufacturer expresses the ratio as produced water / wastewater or in the reverse order.

See also: RO systems with low wastewater production .

How much does an RO system really cost?

You need to distinguish the purchase price from the total operating cost.

This is why two RO systems sold at the same price can have very different operating costs over several years.

What maintenance should you plan for?

Maintenance is essential to preserve the performance of your reverse osmosis system.

In particular, you need to monitor:

• the pre-filters;
• the membrane;
• the post-filters;
• any remineralization filter cartridge;
• the output flow rate;
• the TDS of the produced water;
• the manufacturer's recommendations.

For a detailed guide: how to maintain your RO system .

See also: our RO system maintenance kits .

What are the alternatives to reverse osmosis?

Your choice of technology depends primarily on what you want to change in your water.

To learn more: what is ultrafiltration? .

Does an RO system meet your needs?

Compare flow rate, wastewater production, system type, maintenance, space requirements, and the cost of consumables before choosing a model.

Frequently asked questions before buying an RO system

Is an RO system really worth it?

It depends on your goal. An RO system can be useful if you want to significantly reduce mineral content and many dissolved substances. It is less suitable if your only goal is, for example, to change the taste of your water.

What are the main disadvantages of an RO system?

The main drawbacks are wastewater, maintenance, the cost of consumables, mineral reduction, and the space requirements of some systems.

Does an RO system waste a lot of water?

Not all RO systems have the same water efficiency. The amount of wastewater depends on the membrane, pressure, unit design, and operating conditions. You therefore need to compare the data for the specific model.

Does RO water contain minerals?

Reverse osmosis significantly reduces the concentration of many dissolved minerals. A remineralization filter cartridge can be added after the membrane if this matches your preferences.

Tank-based or direct-flow RO system?

A tank-based system stores a quantity of water in advance. A direct-flow system produces water on demand. The choice depends primarily on your desired flow rate, available space, and budget.

How long does an RO system last?

The unit's lifespan depends on its design and maintenance. The filters and membrane are consumables and must be replaced independently of the lifespan of the system itself.

Can a conventional filter replace an RO system?

It depends on what you want to treat. A carbon filter and a reverse osmosis membrane do not work in the same way. You therefore need to choose the technology based on your water quality and desired result.

About this guide

This guide is written by the Josmose team based on our experience with water treatment solutions and the technical specifications of the different technologies.

Josmose sells RO systems and consumables that you can access from this page.