Water treatment for kitchen and home

Reverse Osmosis Systems for Home

Learn how reverse osmosis works, what an RO drinking-water filter can reduce and which system type best fits your kitchen, household and daily water needs.

Reverse osmosis guide

Choosing a reverse osmosis system for home

Before buying, compare more than price and the number of filter stages. System type, purified-water output, concentrate water, filter life, operation, available space and kitchen installation all matter.

01
The osmosis principle

How does a reverse osmosis system work?

Natural osmosis moves water through a semipermeable membrane towards a more concentrated solution. Reverse osmosis applies pressure in the opposite direction: some water passes the membrane as permeate, or purified water, while retained substances leave in a separate concentrate stream. Pre-filters protect the membrane and post-treatment refines the water for everyday use.

1. Pre-filtration

Reduces sediment and chlorine-related taste or odour while helping protect the membrane.

2. Pressure and membrane

Pressure moves pretreated water along the RO membrane; part of it passes as permeate.

3. Concentrate stream

Retained substances are carried away instead of accumulating in the drinking-water stream.

4. Post-treatment

Finishing filters and remineralization can support a more balanced taste.

02
RO drinking-water filter

What can reverse osmosis reduce?

An RO membrane can substantially reduce many dissolved and particulate constituents. The reduction of any specific substance depends on its size, charge and concentration as well as membrane type, pressure, maintenance and test conditions. General membrane capability is not automatically a performance certificate for every device.

Hardness and saltsincluding calcium, magnesium, sodium, nitrate and sulphate ions
Selected heavy metalssuch as lead, copper or cadmium
Fine particlessediment, rust particles and, depending on size, microplastics
Organic residuesselected pesticides, PFAS and pharmaceutical residues may be reduced depending on the compound
Taste and odouractivated-carbon pre-treatment helps reduce chlorine and selected organic compounds
Microorganismsmembranes form a barrier to many microorganisms, but hygiene and maintenance remain essential
Two solutions for home

Under the sink or on the countertop.

Drop integrates discreetly into the kitchen and treats water by direct flow. Pearl offers flexible placement without a fixed water connection.

BLACKWATER Pearl countertop reverse osmosis system and Drop beneath the kitchen sink
BLACKWATER Pearl on the countertop and BLACKWATER Drop beneath the sink.
Two systems. One clear goal.

Choose the system that fits your life.

Built into your kitchen

BLACKWATER Drop

€1,497 or €1,867 with installation
BLACKWATER Drop under-sink reverse osmosis system

A direct-flow under-sink system with no storage tank. Open the dedicated stainless-steel tap and Drop treats the water in real time.

  • Up to 2.2 litres per minute
  • Compact direct-flow design, no storage tank
  • PCB filter: typically 6–12 months
  • RO membrane: typically 12–24 months
  • Dedicated stainless-steel drinking-water tap
Freedom without plumbing

BLACKWATER Pearl

€1,497
BLACKWATER Pearl portable countertop water system

A countertop 3-in-1 system for filtered, heated and cooled water. Fill the tank, connect the power and select your preferred temperature and volume.

  • No fixed water connection required
  • 5-litre raw-water tank and approx. 1.6-litre carafe
  • Nine temperature settings from 10–98°C
  • Selectable volume from 90–500 ml
  • Suitable for home, office or securely positioned travel use
Explore Pearl
03
After the membrane

Remineralization of reverse osmosis water

The membrane reduces both unwanted substances and much of the dissolved mineral content, which can leave RO water tasting very neutral. A remineralization stage conditions the water and can add selected minerals for a more balanced taste. The contribution varies with cartridge, flow, contact time and source-water chemistry.

BLACKWATER Drop and Pearl include post-treatment. Current product documentation remains the authority for the exact cartridge configuration and product-specific measurements. Read more in our remineralization guide.

04
Permeate and concentrate

Purified water, wastewater and total water use

Reverse osmosis needs a concentrate stream to carry retained substances away from the membrane. BLACKWATER states the values as purified water to concentrate water.

Inlet pressure

Low or unstable pressure can reduce output and efficiency.

Water temperature

Cold water passes through the membrane more slowly.

Water chemistry

High hardness and dissolved-solids levels place greater demand on the membrane.

Filter condition

Loaded pre-filters or an ageing membrane affect both flow and ratio.

BLACKWATER Drop1 : 0.5

2.2 L purified water per minute at 2 bar inlet pressure and 20°C water temperature.

BLACKWATER Pearl1 : 0.25

4 L purified water from 5 L inlet water at 20°C water temperature.

05
Flow and demand

How much output does your household need?

Required output depends on household size, cooking habits and whether water is dispensed directly or collected internally. Direct-flow systems benefit from a high tap flow; countertop systems also need to be assessed by tank capacity, refill routine and temperature functions.

FeatureBLACKWATER DropBLACKWATER Pearl
System typeTankless direct-flow under-sink systemCountertop system with manually filled 5 L source-water tank
Purified-water production2.2 L/min at 2 bar and 20°Capprox. 0.34 L/min; 4 L purified water from 5 L at 20°C
Purified water : concentrate1 : 0.51 : 0.25
Dispensingon demand from a dedicated tapselectable 90–500 ml
Best fithigher demand and a clear countertopno fixed water line; heating and cooling
Rated figures apply under defined conditions. Actual output varies with inlet pressure, temperature, water quality and filter condition.
06
Understand cost per litre

Purchase price and total cost of ownership

Total cost includes purchase price, filters and membrane, purified and concentrate water, electricity for pumps or heating and cooling, plus optional installation and service. Compare these costs with actual consumption and current bottled-water spending.

Purchase

Drop and Pearl are each €1,497. Optional Drop installation adds €370.

Drop replacement filters

PCB filter €80, RO membrane €120, bundle €170. Typical intervals: PCB 6–12 months and membrane 12–24 months.

View current prices
Pearl replacement filters

RO membrane €80, PCB filter €120, bundle €170. Actual intervals depend on water quality and use.

View current prices
Water and energy

Include inlet and concentrate water. Pearl also uses energy for treatment, heating and cooling.

Formula

Total cost over the period ÷ litres actually produced = approximate cost per litre.

Price date

Filter prices checked on 3 September 2026. Current BLACKWATER Shop prices always take precedence.

07
Reverse osmosis in the kitchen

Installation: under the sink or no fixed connection?

Drop under the sink

  1. Check cabinet space, power, cold-water supply and drain access.
  2. Shut off the supply and fit the inlet connection as instructed.
  3. Connect the concentrate line correctly to the drain.
  4. Fit the dedicated stainless-steel tap in a suitable opening.
  5. Flush the system and test every connection for leaks.

Use a qualified installer where experience, connection type or local rules make professional work advisable. Drop is available with installation.

Explore Drop installation

Pearl on the countertop

  1. Choose a stable, level, ventilated surface near a suitable socket.
  2. Remove and clean the source-water tank, then fill it with suitable tap water.
  3. Prepare and flush the unit according to the manual.
  4. Select temperature and dispensing volume.
  5. Clean tanks, outlet and drip tray regularly.

No fixed water connection is required, but clearance and electrical-safety instructions still apply.

Explore Pearl countertop system
08
Reverse osmosis system comparison

Which is the best reverse osmosis system for your home?

The best system is not automatically the one with the most stages. Drop better suits an integrated kitchen, higher demand and direct dispensing from a dedicated tap. Pearl often fits rented homes, offices, flexible placement and users who want heated and cooled water. Start with your use case and installation space, then compare features.

09
Make a balanced decision

Advantages and disadvantages of reverse osmosis systems

Advantages

  • Reduces a broad range of dissolved substances and fine particles.
  • Freshly treated water available at home.
  • Less bottled-water purchasing, transport and storage.
  • Choice of direct-flow or flexible countertop installation.
  • Post-treatment and remineralization support balanced taste.

Points to consider

  • A concentrate or wastewater stream is produced.
  • Filters and membrane need periodic replacement.
  • Hygienic cleaning and maintenance remain essential.
  • Depending on the system, power, space or installation is required.
  • Performance depends on inlet water and operating conditions.
Technical basis

Product testing by Wasserproben Lab GmbH. The laboratory is accredited to DIN EN ISO/IEC 17025:2018 for the scope listed in certificate annex D-PL-21499-01-01. Editorially updated: 3 September 2026.

View laboratory reports and testing basis
BLACKWATER Pearl water system in a modern motorhome
Water freedom on the road

Pearl goes where you go.

Because Pearl needs no fixed plumbing, it can be used in a motorhome with a suitable stable power supply. Position and secure the unit on a level, ventilated surface before use and follow the operating manual while travelling.

Explore Pearl
Side-by-side

Drop or Pearl?

Feature Drop Pearl
Placement Under the sink On a countertop
Water connection Fixed connection No fixed connection
Storage tank None—direct flow Refillable 5 L tank
Heating and cooling No Yes
Best for High daily volume and integrated kitchens Flexible placement, rented homes and travel
Filter interval Approx. 6–24 months by cartridge Approx. 6–24 months by cartridge
Confidence included

Clear delivery, return and support terms.

Documented quality

Product-specific information and available test documentation help you understand the treatment technology and its intended performance.

Delivery across Europe

Germany: free from €200, otherwise €7. Other European countries: €17.

Shipping details

14-day returns

Return an unused, undamaged product within 14 days under the stated return conditions.

Return policy
Questions, answered

Everything important before you decide.

Which reverse osmosis system is right for my home?

Drop is designed for integrated direct-flow use beneath the sink. Pearl sits on the countertop, needs no fixed water connection and offers selectable water temperatures. Your available space, daily demand and installation preference determine the better fit.

Does reverse osmosis remove every substance?

No treatment technology should be described as removing absolutely everything. Performance depends on the substance, inlet water, maintenance and verified test conditions.

Do the systems add minerals?

Both systems include post-treatment intended to condition the water and support a balanced taste. See the product documentation for the exact configuration.

How often are filters replaced?

Typical intervals are 6–12 months for PCB stages and 12–24 months for the RO membrane. Usage and inlet-water quality can change these intervals.

Which system works in a rented apartment?

Pearl is the simplest option when you do not want a fixed water connection. Drop is designed for permanent under-sink integration.

How much wastewater does reverse osmosis produce?

Reverse osmosis separates a purified-water stream from a concentrate stream. Drop provides a purified-water-to-concentrate ratio of 1:0.5 at 2 bar and 20°C. Pearl provides 1:0.25, producing 4 litres of purified water from 5 litres at 20°C.

Is reverse osmosis water the same as bottled water?

No. Bottled waters vary widely in origin and mineral composition. A home system treats your local inlet water on demand and avoids regular bottle transport and storage.

What does a TDS reading tell you?

A TDS meter estimates the conductivity of dissolved, electrically conductive substances. It can help monitor changes in membrane performance, but it does not identify individual compounds and cannot by itself prove drinking-water safety or the absence of contaminants.

What is the difference between osmosis and reverse osmosis?

Osmosis is the natural movement of water across a semipermeable membrane towards a more concentrated solution. Reverse osmosis applies external pressure to move water in the opposite direction through the membrane.

Is a direct-flow reverse osmosis system noisy?

The pump and internal water movement may be audible while water is being produced. Sound level and run time depend on the model, installation, inlet pressure and flow. There is no continuous water production in standby.

Can reverse osmosis be used with hard water?

Generally yes, provided the inlet water remains within the product specification. High hardness can place greater demand on filters and membrane, shorten service intervals and make appropriate pre-treatment advisable.

What maintenance does a reverse osmosis system need?

Filters and membrane are replaced according to volume, time and system status. Hygienic cleaning, flushing and checks of connections and seals are also important. Always follow the instructions for the individual model.

Your water. Your choice.

Stop carrying bottles. Start enjoying water.

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