Which RO system should you choose? The quick answer

There is no single ideal RO system for every household. A model with a tank may be a good option if your budget is limited or you want a supply of water that is immediately available. A direct-flow model is more suitable if you want to produce water on demand and reduce the space taken up by a tank. If your water pressure is too low, a booster pump may be necessary. Finally, if the amount of wastewater is an important consideration, carefully compare the water efficiency of the different systems.

Which type of RO system suits your situation?

Before you choose: how does an RO system work?

An RO system uses a semipermeable membrane. Under pressure, some of the water passes through this membrane, while another portion carries some of the retained substances to the drain.

The system generally includes several pre-filtration stages, including a sediment filter and activated carbon, to protect the membrane and improve overall filtration.

Final performance depends on factors including the membrane used, inlet pressure, water temperature, water composition, and system maintenance.

To understand this technology in more detail: read our guide to reverse osmosis .

1. Which flow rate should you choose for your RO system?

Flow rate indicates how much water the system can produce over a given period. It may be expressed in liters per hour or GPD (gallons per day).

To make the right choice, you need to distinguish between the membrane's theoretical capacity and the amount of water actually available at the faucet. Actual performance may vary depending on the pressure, temperature, and quality of the water being treated.

Questions to ask yourself

• How many people use this water every day?
• Will the RO water be used only for drinking?
• Will it also be used for cooking?
• Do you need to fill large pitchers quickly?
• Would you like a stored water supply?

2. Tank-based or direct-flow RO system?

Both technologies can produce RO water. The main difference is how this water becomes available at the faucet.

For more details: direct-flow or tank-based RO system: what are the differences?

3. How do you compare wastewater?

Some of the water supplied to an RO system is used to flush away the substances retained by the membrane. Water efficiency varies from one system to another.

Manufacturers often present this efficiency as a ratio. However, you need to check which convention is used: some indicate the ratio of produced water / wastewater, while others may present it in the reverse order.

It is therefore better to compare systems using clearly defined data rather than simply comparing two ratios without checking what they mean.

See also: our low-wastewater RO systems .

4. Do you need a booster pump?

A reverse osmosis membrane needs sufficient pressure to operate properly.

When the supply pressure is too low, a booster pump can help the system operate under better conditions. In particular, it can help maintain the flow rate and operation intended by the manufacturer.

However, the minimum pressure and recommended operating pressure depend on the model. You should therefore always check the system's technical specifications before purchasing.

5. Should you choose an RO system with remineralization?

Reverse osmosis greatly reduces the amount of many dissolved substances in water, including some of its minerals.

Some users therefore choose to add a remineralization filter cartridge after the membrane. Depending on its composition, it can add certain minerals to the water produced.

Remineralization is therefore not an additional filtration technology: it takes place after reverse osmosis. Its value depends primarily on your preferences and the system you choose.

Learn more: remineralization solutions for RO systems .

6. What maintenance costs should you budget for?

The purchase price represents only part of an RO system's actual cost. Filters, the membrane, and any consumables need to be replaced periodically.

Frequencies may vary depending on water quality, the volume consumed, and the RO system model. The manufacturer's recommendations should therefore take priority.

Also read our guide: how to maintain your RO system .

For consumables: see maintenance kits for RO systems .

7. How much space should you allow under your sink?

Before ordering an RO system, measure the space actually available under your sink.

You need to account for the system's dimensions as well as:

• the tank, if there is one ;
• the access needed to change the filters ;
• the tubing and connections ;
• the electrical supply if a pump is used ;
• access to the faucet and drain.

A compact system may be easier to fit, but its performance must still meet your needs.

7 criteria to check before buying

Can reverse osmosis reduce PFAS?

PFAS are a large family of chemicals that are particularly persistent in the environment.

Reverse osmosis is one of the technologies used to reduce the concentration of certain PFAS in water. However, actual performance depends on factors including the membrane, the pre-filtration system, the characteristics of the inlet water, and proper maintenance of the installation.

It is therefore better to consult the documented performance of the system being used rather than assume that all RO systems will deliver exactly the same results.

To explore this topic further: our in-depth article on PFAS filtration .

Still deciding between several models?

See our detailed comparison to compare specifications and identify models suited to your needs.

Frequently asked questions about choosing your RO system

How do you choose a home RO system?

Focus on comparing flow rate, operation with or without a tank, required pressure, water efficiency, remineralization, maintenance costs, and dimensions. The right model then depends on the number of users and your daily water consumption.

Tank-based or direct-flow RO system: which should you choose?

A tank-based model stores water in advance, while a direct-flow RO system produces water on demand. A tank can be useful when you want a quantity of stored water immediately available. Direct flow eliminates the need for this storage and can be more compact.

Does an RO system need a pump?

That depends on the supply pressure and the model you choose. When pressure is too low, a booster pump may be needed to allow the membrane to operate under the conditions specified by the manufacturer.

Which RO system should you choose for a family of four?

Your main priority should be choosing a flow rate that meets your daily water consumption. If several liters need to be available quickly, a high-flow system or a system with stored water may be more suitable. Then compare maintenance, wastewater, and available space.

Should you remineralize RO water?

This is not required for reverse osmosis to work. However, some users choose a remineralization filter cartridge to add certain minerals after filtration. The choice depends on the system and your preferences.

How much does RO system maintenance cost?

The cost depends on the number of filters, how often they need to be replaced, the price of the membrane, and any additional filter cartridges. It is therefore useful to compare consumable costs before purchasing, as well as the price of the system itself.

How long does a reverse osmosis membrane last?

Its service life varies depending on the membrane, water quality, the volume treated, pressure, and pre-filter maintenance. The manufacturer's recommendations should be used as your reference.

Does reverse osmosis reduce PFAS?

Reverse osmosis can reduce the concentration of certain PFAS. The level of reduction depends on factors including the membrane, pretreatment, and operating conditions. You should therefore refer to the documented performance of the specific system.

Sources and transparency

This guide was written by the Josmose team based on the technical specifications of reverse osmosis systems and our experience distributing water treatment solutions.

Josmose sells RO systems and some of the products mentioned or accessible from this page.