Under Sink Water Filters

Under-sink water filters are an effective solution for anyone who values pure, tasteless and safe drinking water - without taking up space on the worktop. Unlike countertop water filters, these systems are installed directly under the sink and connected to the cold water pipe. The filtered water is then drawn off via a separate or integrated tap.

A major advantage: under-sink water filters often work with multi-stage filter systems that reliably remove pollutants such as chlorine, heavy metals, microplastics or pesticide residues from the water. At the same time, important minerals are retained. Investing in such a system is particularly worthwhile for households in regions with contaminated tap water or sensitive taste buds. Modern models are also easy to maintain and can be customized with replaceable filter cartridges.

An under-sink osmosis system from Klarstein is a highly efficient water filter system that is permanently installed under the sink. It uses the principle of reverse osmosis to remove even the finest impurities from tap water. The water is pressed through a semi-permeable membrane at high pressure, which almost completely retains pollutants such as heavy metals, nitrate, limescale, chlorine, drug residues, microplastics and even bacteria and viruses.

How reverse osmosis works

The system usually consists of several filtration stages:

• Pre-filter (e.g. sediment filter and activated carbon filter): Remove coarse particles, chlorine and organic compounds.


• Osmosis membrane: The central component filters dissolved substances with a pore size of approx. 0.0001 micrometers.


• Post-filter (e.g. activated carbon post-filter or mineral filter): Refine the taste or re-enrich the water with minerals.

The purified water is drawn off in a pressure tank or directly via a separate tap. Waste water produced during filtering is fed into the drain via a separate connection.

Advantages of an under-sink reverse osmosis system

• Extremely high water purity - ideal for heavily contaminated tap water


• Unobtrusive installation under the sink saves space


• Large selection of variants, e.g. with mineralization, UV disinfection or direct connection to coffee machines


• Improved taste for drinking water, coffee, tea and food preparation

Areas of application

An under-sink reverse osmosis system is particularly useful:

• For dubious tap water


• In regions with high nitrate or pesticide levels


• For households that want to replace pure bottled drinking water


• For allergy sufferers, baby households or people with a weakened immune system

Important notes

Please note during operation:

• Water consumption is higher as part of it is discharged as waste water.


• Regular filter changes are essential for hygiene and performance.


• An additional tap is often necessary, but can be integrated inconspicuously in modern designs.

An under-sink reverse osmosis system is one of the most effective ways of providing yourself with particularly pure drinking water every day - space-saving, reliable and sustainable.

A Klarstein under-sink water filter is a convenient solution for clean drinking water straight from the tap - space-saving and efficient. But not all systems are the same. If you want to benefit from high water quality in the long term, you should pay attention to certain functions that make the filter both efficient and user-friendly.

Multi-stage filter system

A high-quality under-sink water filter should consist of several filter stages in order to specifically remove various pollutants. Common combinations include:

• Sediment filter against suspended particles such as rust, sand or sludge


• Activated carbon filter to reduce chlorine, pesticides, heavy metals and organic compounds


• Ceramic filters or hollow fiber membranes for bacteria and germ retention


• Ion exchanger or limescale filter to reduce water hardness (optional)

Depending on the model, an ultrafiltration or reverse osmosis module can also be integrated.

High flow rate and stable performance

Despite its effective cleaning performance, a good filter should offer a sufficiently high water flow rate - at least 1.5 to 2 liters per minute for pressure filters. A steady flow without pressure loss is particularly important for households with several people.

Long filter service life and easy replacement

Long-life filter cartridges reduce maintenance costs and effort. Ideally, a filter system should only require maintenance every 6 to 12 months - depending on usage and water quality. It should be possible to change the filter without tools and hygienically.

Separate water withdrawal via an additional tap

Many systems discharge the filtered water via a separate under-counter water filter tap next to the mixer tap. Alternatively, there are 3-way taps that combine normal and filtered water in one tap. It is important that the solution matches the kitchen design and is easily accessible.

Tested materials and certifications

A safe under-sink water filter should be made of food-safe, BPA-free materials. Certifications such as TÜV, NSF or LGA are also proof of quality. They confirm compliance with hygienic and technical standards.

Additional functions (optional)

Depending on requirements, some systems offer additional features:

• Mineralization units for enrichment with magnesium or calcium


• UV filter for additional germ elimination


• Filter change indicator (manual or electronic)


• Bypass valves to bypass the filter during maintenance

A good under-sink drinking water filter impresses with its multi-stage cleaning system, high flow rate, simple maintenance and tested quality. Depending on requirements (e.g. for an under-sink water filter in the kitchen), additional functions can further increase convenience and water quality. If you pay close attention to these features, you can be sure of fresh and healthy drinking water straight from the tap.

An under-sink water filter from Klarstein is an excellent solution for obtaining permanently clean and tasty drinking water directly from the tap. To find the right system for your household, there are a few important criteria that you should consider before buying:

Type of filter system

Depending on which impurities you want to remove from your tap water, different technologies make sense:

• Activated carbon filter - good for chlorine, taste, odor and organic substances


• Sediment filter - removes coarse particles such as sand, rust or dirt


• Reverse osmosis - very thorough, also for heavy metals and dissolved substances


• Ceramic or hollow fiber filter - reduces microorganisms and the finest particles

Tip: Check your tap water profile before buying or have it analyzed to choose the right filter type.

Filter performance & flow rate

An under-sink filter should let enough water through per minute without noticeably reducing the pressure at the tap. A high flow rate is particularly important in larger households so that the filtered water is quickly available even when filling several glasses at the same time.

Care & maintenance

Filters must be changed regularly to maintain performance:

• Pay attention to simple and clear filter change intervals (e.g. 6-12 months)


• Check whether the change can be carried out without tools and without specialist knowledge


• Some systems have filter change indicators or reminder apps

This makes maintenance more convenient and prevents the system from suffering or clogging.

Space requirement & installation

Under-sink filters are installed under the sink. You should check before buying:

• Space under the sink: height, width and depth dimensions fit?


• Connection options: suitable cold water pipe and drain


• Faucet included: some systems require a separate faucet

Some models also offer 3-way taps that can control filtered and unfiltered water via one tap - this saves space.

Materials & certifications

High-quality materials ensure durability and hygienic safety:

• Food-safe components without harmful substances (e.g. BPA-free)


• Certifications such as NSF, TÜV or international drinking water standards


• Manufacturer's information on filter performance and pollutant reduction

Certificates provide certainty about the actual effectiveness.

Additional functions & convenience features

Depending on your needs, additional functions can be helpful:

• Mineralization stage for a better taste experience


• UV disinfection to kill germs


• Smart displays or app connection for filter monitoring

Such extras improve convenience and water quality, but are not always necessary.

When buying an under-sink water filter, you should consider the filter principle, ease of maintenance, space requirements, performance and quality certificates. The better you know your expectations and your tap water, the easier it will be to find a system that delivers clean, healthy and tasty drinking water in the long term - without plastic bottles and with minimal effort.