Reverse osmosis water filters have gone through tremendous change since their humble beginnings. These changes reflect the need for simpler, yet performant, and more modern water filtration solutions.

Manufacturers of modern RO systems have sought to make these filters more efficient and have eliminated some of the bulky hardware that were so defining of traditional RO filters.

In what follows, we will share a comparison between two of the newest additions to the RO filter landscape – the direct flow RO system and the zero installation RO system to determine which offers the best user experience and the best-quality drinking water at the most reasonable price.

We’re comparing efficiency, contaminant removal capacity, filtered water output, and costs both in terms of initial purchase cost and maintenance.

So, here we go:

What are Direct Flow RO Systems?

If you’ve seen reverse osmosis filters before, you probably have an idea about their make-up — multiple filter cartridges, each representing a stage of filtration and a reverse osmosis tank that stores filtered water.

Direct flow RO filters eliminate the need for a reverse osmosis tank. Without a storage tank, water is no longer stored after filtration, and it’s filtered promptly as you turn on the tap to pour yourself a glass of water.

A direct flow system or tankless reverse osmosis filter has offered a solution to three setbacks of traditional RO systems – back pressure, water freshness, and bulky hardware issues.

As you’ll see below, tankless RO filters are far superior to the classic system that’s based on the 3-step process of filtration followed by storage and then consumption.


What are Zero Installation RO Systems?

Zero installation RO water filters take things a step further – no installation, which means that there is no need for incoming water pressure. This adds a completely new dimension to RO filters in the sense that there’s no need for plumbing and you now have the advantage of portability.

Zero installation reverse osmosis filters can be placed anywhere without any need for plumbing. However, compared to traditional plumbed-in systems, these new RO models require electricity to operate.

Let’s see how these two systems compare and which one should be your top pick if you’re considering upgrading your old system or you’re buying a filter for the very first time.


The Comparison: Tankless System vs Zero-Plumbing System

For the purposes of this comparison, we’ve chosen a product that best represents the typical features of each type of RO system we’re discussing.

To illustrate the features of a tankless RO filter, we’ve chosen the Osmio D7 Direct Flow Reverse Osmosis System and to illustrate the features of the zero installation RO filter, we’ve chosen the Osmio Zero Installation Reverse Osmosis System.


Osmio D7 Direct Flow RO Water Filter

A sleek and stylish model, this tankless RO filter fits nicely under counter, taking up very little space.



  • 5-stage filtration (3 pre-filters, a 400 GPD membrane, alkaline filter);
  • Smart Water capabilities (built-in filter lifetime tracking system, water analysis tool);
  • Direct flow, no tank model for maximum water freshness;
  • 6 to 24 months filter lifetime (24 months for the RO membrane, 6 months for the rest);
  • No maintenance, no back pressure for less waste;
  • Installed under the kitchen counter;
  • Dispatched with a high-quality filter tap;
  • Easy assembly and filter changeover.


Filtered water output:

The Osmio D7 produces 1000 litres of tasty alkaline water per day.


Contaminant removal:

This tankless RO model removes the following contaminants:

  • Bacteria like E-Coli and viruses;
  • Sediments, limescale, dissolved solids;
  • Hormones, pharmaceuticals;
  • Chlorine, fluoride, nitrates, and heavy metals.


Osmio Zero Installation RO Water Filter

By the look of it, this Osmio filter seems more like a fancy coffee machine than a reverse osmosis water filter, yet it’s a highly performant countertop RO filter that also dispenses hot and boiling hot water, rendering your old kettle useless.


  • No need for installation, simply assemble, plug in and see it in action;
  • 4-stage filtration process;
  • No connection to water supply needed;
  • Dispenses ambient water, hot water and boiling hot water;
  • Easy to use, simply pour water into the dedicated compartment and wait for the filtration cycle to complete;
  • On-the-counter use;
  • Easy filter replacement (twist-off filters);
  • 6 months filter lifetime for all filters;
  • Fully portable;
  • Automatic switch-off to save power.


Filtered water output:

This no-installation filter from Osmio has a daily filtered water output of 7.8 L per hour.


Contaminant removal:

In terms of contaminant removal, you can count on this filter to solve the following drinking water contamination issues:

  • Sediments, chlorine, limescale, organic impurities;
  • Bacteria & Viruses;
  • Other pollutants.


Which is Best?

When it comes to purchase costs the zero installation RO filter from Osmio is the more affordable option.

However, since all filters in this system (including the membrane) are replaceable every 6 months, its maintenance costs are a bit higher as opposed to the maintenance costs of the direct flow system.

Osmio’s direct flow RO system is pricier, however, its annual maintenance costs are lower, and it offers pH optimised water directly from the tap, something that lacks in the zero-installation filter.

No doubt the portable RO filter is easy to use, offers ambient water and boiling water, and it can be placed anywhere in your home or office. It also looks extremely good.

Still, if you’re looking for a system that offers instant filtration and you don’t mind having to install a water filter, the tankless reverse osmosis filter is your best option.



Water filters are constantly evolving and transforming. Something that today doesn’t seem possible, becomes a reality the next, making you forget about everything you thought you knew about filters.

Tankless RO systems and portable RO filters are replacing and outperforming traditional systems and becoming more affordable as new technologies emerge and consumer needs shift towards more elegant and high-tech solutions.

If you want a performant residential filter, but don’t like the idea of bulky hardware or you don’t have enough space to accommodate bulky hardware, today’s RO water filters are an elegant, high-performing and compact alternative to traditional models.


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