To choose the ideal RO unit for your needs, you need to ask yourself the right questions. The aim of this article is to guide you through 6 essential questions to ask yourself in order to arrive at the optimum choice. If you're still unsure, contact Aquacycle.eu - we're here to answer your questions.

1. What is the initial quality of the water I want to filter?

• Origin :
  • If the water comes from a well or a spring, please contact us directly by e-mail so that we can guide you through the appropriate analyses.
  • If the water comes from the mains, you :
    • You can buy an Aquacycle.eu PPM test which will tell you the dry residue of your water in an instant.
    • Find complete water analyses online, depending on your supplier. You'll see all the contaminants that osmosis eradicates (nitrates, lead, chlorine, fluoride, etc.), as well as water hardness (limescale content).
• Hardness : Water hardness refers to the level of calcium and magnesium that can precipitate as limescale deposits. Above 25°f hardness, we recommend installing a softener (salt, CO2 or magnetic) or at least a Scalex system.

Reducing hardness before filtration allows :

• The membrane operates more efficiently, with improved osmosis water production and optimized waste discharge.
• Reduce membrane replacements, thus cutting operating costs.
• Board The following is a list of the two factors you need to be aware of in order to better understand why you want to filter your water, and what your specific needs are.

2. Direct-flow or tank Osmosis?

An osmosis plant can feed a tank or directly into your tap, known as direct flow. Here are the advantages and disadvantages of direct flow:

• Advantages :
  • Eliminate stagnation: RO water is produced in real time, guaranteeing optimum quality. If your osmosis unit is often shut down for more than 3 days at a time, which promotes bacteriological growth, a direct-flow osmosis unit will save you from having to purge your tank.
  • Space-saving: No tank means significant space savings under your sink. Dimensions of a useful 7l tank are 35 x 26 x 26 (L x W x H).
  • Production capacity: The fastest direct-flow reverse osmosis plants produce up to 3l / minute, which is higher than 2.5l / minute, which corresponds to the outflow from a tank.
• Disadvantages :
  • More expensive: The system requires a more powerful pump and a larger diaphragm, which increases the price of the unit.
  • Production capacity: The slowest direct-flow reverse osmosis systems produce less than 2.5l/minute, which corresponds to the output of a tank. If you don't want to invest in a top-of-the-range unit, but need small quantities of RO water quickly, you'll save time with a tank.

Board To help you find your way around, take a look at our product comparison.

3. Number of filtration steps?

Reverse osmosis systems often vary from 3 to 8 filtration stages. Some of these stages come before the osmotic membrane, known as pre-filters, while others come after. These are called post-filters. Below is a summary table:

Potential stages (#)	1	2	3	4
Type	Pre-filter	Pre-filter	Pre-filter	Osmosis
Name	PP - 100% Polypropylene	GAC - Charcoal granules	CTO - Compact coal	Osmotic membrane
Filtration efficiency	5 microns (µm)	1 micron (µm)	0.5 microns (µm)	0.0001 microns (µm)
Filtered elements	Sand, rust, fine sediments	Fine sediment	Bacteria	Bacteria, virusses, dissolved heavy metals, pesticides, PFAS, nitrates,

Potential stages (#)	5	6	7	8
Type	Post-filter	Supplement	Supplement	Supplement
Name	Activated carbon	Remineralization	UV lamp	Alkaline filter
Filtration efficiency	Taste & smell	Bioavailable mineral supplements: Magnesium, calcium, potassium	Viruses & bacteria	Increases water PH from (PH <7) to (8<PH <10)
Filtered elements	Tastes and odors that may be related to osmosis	NA	Living elements. Relevant after stagnation in reservoir	NA

Board More steps doesn't necessarily mean better results. On the contrary, more steps mean more maintenance and therefore higher costs. That's why Aquacycle.eu's selection focuses on simple, effective models, concentrating primarily on the efficiency of osmosis. All supplements can then be easily added to suit individual needs.

4. Is it difficult to maintain?

The aim of pre-filtration is to roughen up the work in order to optimize the performance and longevity of the osmotic membrane:

• Pre-filtration :
  • Less expensive
  • Maintenance 4-12 months
• Osmotic membrane :
  • More expensive
  • Maintenance 24-36 months
• Post-filters: Varies according to the stage in question

Advice :

• Direct-flow models are often the easiest to maintain, with compact cartridges that combine the pre-filtration stages.
• Aquacycle.eu makes maintenance easy by offering complete maintenance kits for each osmosis unit in its range.

5. How much water does my reverse osmosis unit discharge?

A reverse osmosis filter systematically rejects a certain quantity of water per liter of filtered water. The ratio of pure water to rejected water to purchase depends mainly on two factors:

• Inlet water pressure: An osmotic membrane operates at its optimum between 4-6 bars of pressure. Below 3 bars, efficiency drops and the portion of water rejected increases considerably. Models without electricity are resilient, but entirely dependent on circuit pressure. Electrified models, on the other hand, are fitted with a pump to achieve the pressure required for ideal efficiency.
• Osmotic membrane size: Generally speaking, the larger the membrane, the higher the flow rate for lower rejection.

Please note: This article focuses on factors influencing the rejection rate at the time of purchase. The rejection rate is also influenced by the quality of the water supply and maintenance.

The pump and membrane size are the two major factors influencing the price of an osmosis plant. A low-rejection (and often high-flow) osmosis plant will therefore often be more expensive.

Board If you're concerned about the environment, this is an important factor to consider. Be careful, it will influence the initial investment. Consult our product comparison to better understand the total cost of your installation in terms of cost/liter.

6. What is the total cost of my osmosis unit?

When making a purchase, it is important to consider not only the initial investment, but also the costs associated with filtration, in order to arrive at a total cost and profitability:

• Total cost = purchase + maintenance + water consumption
  • Purchase price = initial investment
  • Maintenance = Maintenance costs
  • Water consumption = filtered water + rejected water

You can find the total cost of each Aquacycle.eu osmosis unit in our product comparison.

Board By comparing the total cost of an osmosis unit with the price of an equivalent volume of bottled water, it's possible to estimate the return on investment. To find an estimate of the profitability of Aquacycle.eu products, please consult the article "Network or bottle: ecology and profitability."

Conclusion

A well-chosen reverse osmosis system can considerably improve the quality of your water and, by extension, your health. The key is to make an informed choice. If this 6-question guide doesn't answer all your questions, please contact us.

Related article:

• Reverse osmosis fundamentals
• What's the difference between reverse osmosis and an ultrafilter?
• Is osmosis water too pure?
• Network or bottle? Ecology and profitability
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