More and more kitchens incorporate a reverse osmosis system to have filtered water ready to drink or cook without depending on jugs. But installing osmosis is only half the job: the sink tap also has to be prepared to deliver that filtered water separately from the usual hot and cold water. In this article we explain, in a general and verifiable way, what a domestic reverse osmosis is, why it needs a three-way tap and what differentiates a tap dedicated only to osmosis from a combined one that integrates both uses.
Quick answer
Yes: a domestic reverse osmosis system almost always needs a tap with an independent path for the already filtered water, in addition to the hot and cold water. It can be a small tap dedicated only to osmosis or a combined kitchen tap that integrates normal use and the osmosis outlet in the same body, like the models you will find in the NOLUXA kitchen collection.
In this article
What is a home reverse osmosis system?
Reverse osmosis is a filtration technology that passes tap water through a semi-permeable membrane, along with several pre-filters and, in most household equipment, a carbon post-filter. The result is water with a notable reduction in dissolved salts, particles and other elements present in the inlet water, specifically designed for oral water: that which is drunk, used for cooking or for ice and infusions.
A typical domestic osmosis unit is installed under the sink, connected to the cold water supply, and usually includes a small accumulation tank to have filtered water available immediately, without waiting for the membrane to filter in real time. It is a periodic maintenance system: the prefilters and the membrane are replaced according to what the equipment manufacturer indicates, not the taps.
This article focuses on the part that you will find confirmed in our catalogue: the kitchen taps prepared to work with these systems. We do not sell the osmosis equipment itself, so if you are looking for the under sink filter you will have to purchase it from a water treatment specialist; What we can help you choose wisely is the tap that will deliver that filtered water to your sink.
Why you need a three-way tap
A conventional kitchen tap manages two inputs: cold water and hot water, which are mixed in a single spout using the single-lever mixer cartridge. When an osmosis device is added, a third water circuit appears completely independent of those two: the already filtered water, which should not mix with the cold or hot water from the network at any point in the tap.
That is why the tap needs, at least, a third internal passageway with its own differentiated outlet, whether it is an exclusive spout, an independent nozzle or a diverter that physically separates the filtered circuit from the mains water circuit. Mixing both circuits within the same body of the tap, without a separate path, would nullify much of the point of having the osmosis equipment, because the filtered water would once again be in contact with the unfiltered water before leaving the glass.
General installation concept, not a flow figure.
Internal differences from a standard tap
At the installation level, a normal kitchen tap only needs two flexible connectors, one for cold and one for hot. An osmosis-prepared tap adds a third flexible connector or hose, usually smaller in diameter, that connects directly to the filtered water outlet of the osmosis equipment installed under the sink. That third connection is what makes the real difference compared to a conventional sink tap, and it is the first thing to check that the under-sink cabinet has space to accommodate it without problems.
Dedicated osmosis taps versus combined taps
In general terms, there are two different approaches on the market to solve this third water circuit, and it is advisable to be clear about them before purchasing because they change both the installation and the final result on the countertop.
The first is the tap dedicated only to osmosis: a small tap, independent of the usual sink tap, which is installed next to it and whose sole function is to deliver filtered water. The second is the combined tap, which integrates in the same body the normal use of the sink (hot and cold, with its cartridge and its spout, often pull-out) and the osmosis water outlet, so that a single tap solves both general washing and use as well as filtered water, without the need to drill a second hole in the countertop for an additional tap.
| Aspect | tap dedicated only to osmosis | combined tap (normal + osmosis) |
|---|---|---|
| Holes in countertop | You need an additional one, apart from the main tap | Only one, the one from the kitchen tap itself |
| sink tap | The one you already have is kept, without touching it | Replaced by the combined model |
| Aesthetics on the countertop | Two visible taps | A single tap, visually cleaner |
| When is the best fit? | Reforms where you do not want to change the current tap | New kitchen or when it's time to renew the tap anyway |
How this differs from connecting a filter to a standard tap
A common question is whether it is worth installing the osmosis equipment under the sink and simply connecting it, without a third water circuit, to the normal kitchen tap that is already installed. Technically, if the tap only has two internal routes (hot and cold), this direct connection is not viable without modifying the tap, because there is no independent path through which the filtered water can leave without mixing with the mains water that remains in the body of the tap itself or in the shared spout.
The alternative seen in some improvised installations is to leave the filtered water outlet in a separate tap, such as a stopcock, without integrating it into the sink tap. It works, but it gives up the convenience of having a single well-identified filtered water point, and in many cases it ends up being less practical on a daily basis than a tap originally designed for this function, whether dedicated or combined.
Therefore, when installing osmosis from scratch, the most common thing is to directly plan what type of three-way tap to use, instead of trying to later adapt a tap that was not intended for it.
Important
The connection of an osmosis tap to the filtration equipment must be done by an installer or plumber, respecting the instructions of the osmosis equipment manufacturer and checking the tightness of the three connections before completing the installation. A poorly tightened flexible connector in the osmosis line can cause leaks under the sink just like any other water connection.
Reverse osmosis kitchen taps in the NOLUXA catalogue
At NOLUXA, as official distributors of IMEX, we have several models of kitchen taps prepared originally for osmosis, of the combined type: they solve the normal use of the sink and the filtered water outlet in the same body, with a pull-out spout for everyday use.
| Model | Available finishes |
|---|---|
| Lazio pull-out osmosis kitchen taps | Chrome, brushed rose gold, brushed gold, brushed nickel, matt black, Black Gun Metal |
| Pull-out osmosis kitchen taps, Split series | Chrome, matt black, brushed gold |
| kitchen taps Marsella osmosis | matt black |
The three models share the same logic: a pull-out spout for regular use of the sink and a third integrated way to connect the osmosis equipment that you have or are going to install under the furniture. The difference between them is in the design of the body and spout, and in the range of finishes available in each series, so that you can adjust the tap to the rest of the taps and the kitchen appliances.
What to check before buying
Before deciding on an osmosis tap for your kitchen, it is worth reviewing a few points:
- Confirm if you need a tap dedicated only to osmosis (compatible with the sink tap you already have) or a combined tap that replaces the current one and integrates both uses.
- Check how many holes your countertop already has and how many the model you choose requires: a combined tap is usually solved with the existing hole, while a dedicated one requires an additional one.
- Check that the cabinet under the sink has enough space for the osmosis equipment and for the third hose of the tap, without it being under tension or excessively bent.
- Check the finish of the tap against the rest of the taps and metal elements in the kitchen, since in the same space it is advisable to maintain visual coherence.
- Have the osmosis equipment manufacturer's instructions on hand to confirm the connection type of your filtered water outlet before choosing the final tap.
Quick tab
- What is reverse osmosis: membrane filtration that reduces salts and particles from oral water, with equipment installed under the sink.
- Why you need a three-way tap: the filtered water must come out through a circuit independent of the hot and cold water.
- dedicated tap: small, apart from the main tap, it needs an additional hole in the countertop.
- Combined tap: integrates normal use and osmosis in a single body, with pull-out spout.
- NOLUXA (IMEX) models: Lazio, Split and Marsella, all combined type.
- Before installing: check the space under the sink and the osmosis equipment manufacturer's instructions.
How we created this guide
For this article we have started from the product sheet and the actual finishes of the kitchen tap models with IMEX osmosis that we distribute, and general technical knowledge about the operation of domestic reverse osmosis and filtered water installations in homes. We do not describe or sell the osmosis equipment (the under sink filter) because it is not part of our confirmed catalogue; The focus of this guide is exclusively on compatible taps. No own laboratory tests have been carried out.
kitchen taps prepared for osmosis
Discover the Lazio, Split and Marsella models with integrated third water circuit, in the finishes of the NOLUXA kitchen range.
See kitchen tapsSources and references
- technical data sheets and finishes for IMEX kitchen taps distributed by NOLUXA.
- General technical knowledge of domestic reverse osmosis and mouth water filtration.
- NOLUXA Return Policy .
- Contact NOLUXA if you have questions about the compatibility of your osmosis equipment with a specific model.
