Dupla RO 200 reverse osmosis unit supplied assembled, no electricity needed

Regular price $92.00
Regular price Sale price $92.00
$30.66 × 3 with no fees

This reverse osmosis unit is supplied fully assembled, ready to screw onto a cold water tap. Its three stages comprise a 5 µm pre-filter, an activated carbon filter and the membrane.

The unit produces 120 to 200 litres per day without electricity, removing 95 to 98% of dissolved salts.

Ref. 80545·Reverse osmosis unit
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The summary

  • What you receive: the assembled unit, with its three stages in place, its pipes and its tap fitting.
  • What it removes: 95 to 98% of salts, 99% of bacteria, and at most 90% of nitrates.
  • How to choose: this one when you want a ready-assembled unit, with no plug and no adjustment.
  • How much effort day to day: three standard cartridges, replaced once or twice a year.
  • What you need to provide: a tap with a pressure of between 3 and 5 bar, and a drain for the waste water.
  • The water produced: free of minerals, it needs to be prepared before it goes into a tank.

Reverse osmosis unit supplied assembled and needing no electricity, for 120 to 200 litres of osmosed water a day

The Dupla RO 200 is a reverse osmosis unit supplied assembled, which screws onto a cold water tap and works without electricity. It produces 120 to 200 litres of osmosis water per day from water between 8 and 15 °C pushed at 3 to 5 bar. It removes 95 to 98% of salts, but at most 90% of nitrates.

The Dupla RO 200 reverse osmosis unit arrives assembled. The three filter housings are in place, the membrane is inside, the pipes are cut to length: you screw the fitting onto a cold water tap, run the clean outlet to a container and the waste outlet to the sink, and turn on. It needs no power socket, no adjustment, no assembly.

🔬 What the membrane retains

Retention varies by pollutant: 95 to 98% for salts and hardness agents, 97 to 98% for aluminium and sulphates, 95 to 98% for cadmium, 99% for bacteria. It also reveals a limit that no overall figure shows: nitrates and silicates plateau at 90%. A reverse osmosis unit therefore does not remove nitrates the way it removes limescale, and if your mains water is high in them, a tenth will always remain.

Salts and limescale

They are removed at between 95 and 98%. This is the main use, in freshwater as in reef tanks.

Nitrates

They are retained at 90% at most. The rest passes through, and this has to be taken into account with heavily loaded tap water.

🚰 Pressure and temperature

An osmosis unit without electricity has only the pressure and temperature of your mains water to work with. The output, 120 to 200 litres per day, corresponds to water between 8 and 15 degrees pushed at 3 to 5 bar. Outside this range, output departs from the figure: this is normal, and it is why it is given as a range rather than a single value. The unit accepts a maximum of 2 to 6 bar. Check your pressure with a tap pressure gauge before ordering: the measurement takes a minute. Pressure also drops at peak times in some areas, so the reading that matters is the one taken when you will actually be producing water.

Three things to check before buying

Measure your tap pressure, because below 2 bar the unit will produce almost nothing and you will think it is faulty. Next, identify where the waste water goes, which must reach a drain and not a bucket. And never connect a reverse osmosis unit to a hot water supply: the membrane cannot withstand it, and it is the most expensive part of the unit.

Measuring the conductivity of the water produced

The pH, EC and TDS pocket tester measures in a few seconds the conductivity of what comes out of the unit. Take a reading on the day it is commissioned, then from time to time on a container: a value that rises from one month to the next signals a saturated pre-filter or a membrane that is retaining less effectively, well before your tanks are affected. The same device then serves to check the conductivity reached after remineralisation.

🧰 Three cartridges, three references

The first stage is a 5 micron pre-filter that traps sand, rust and particles. The second is an activated carbon block that removes chlorine and organic compounds, and protects the membrane, which cannot tolerate chlorine. The third is the membrane itself. Each of the three has its own replacement part number, so you won't have to hunt for an equivalent when the time comes. The filter housing wrench is supplied in the box, and replacement takes about ten minutes, with the water supply turned off. Note the date of each change: the cartridges should be replaced every 6 to 12 months, and nothing on the unit indicates a clogged pre-filter. You will only see it in the flow rate, which drops sharply while the membrane is still in good condition.

🪣 Filling a container

At 120 to 200 litres per day, the unit produces 5 to 8 litres per hour. A 20-litre container therefore fills in 2 h 30 to 4 hours, and during that time 60 to 80 litres of waste water go down the drain, since 3 to 4 litres are discharged for every litre kept. The unit does not stop on its own when the container is full: choose a container larger than the volume you need, or start production at a time when you will be nearby. The flow restrictor supplied fits on the waste outlet and sets the ratio between the water kept and the water discharged. In aquaponics, this output is enough for the daily top-up of a small system, which you can prepare the day before for the next day; the article on pond evaporation in summer helps you estimate this volume according to the season.

🧂 Remineralising before use

With mains water at 500 µS/cm, a rejection rate of 95 to 98% gives product water of around 10 to 25 µS/cm, in other words practically empty. The simplest way to prepare it is to blend it with tap water: at equal volumes, the hardness, alkalinity and conductivity of the mixture fall to half those of your mains supply, and with 3 volumes of osmosis water to 1 of tap, to a quarter. Nitrates decrease in the same proportion, which is useful where mains water is high in them. Check the mixture with a KH carbonate hardness test and a GH general hardness test before pouring it into a stocked tank, then note the proportions you settle on so that you can repeat the same mixture at every water change.

🌱 The starting water for a system

Starting from osmosis water lets you set the conductivity and hardness of the water in your tanks yourself, rather than depending on the composition of the mains supply. In aquaponics, this unit is mainly used for two things: filling a new system from a known baseline, and topping up for evaporation without concentrating the mains salts season after season. The guide on pH regulation covers what you will then do with this water. Finally, bear in mind that the waste water is more heavily loaded than your tap water: it carries away what the membrane has just stopped, and it has no place in your system. The filter on your tank keeps all of its stages and its filter media, since the reverse osmosis unit only treats the top-up water.

Technical specifications

Production

Maximum output
200 L per dayVaries depending on the quality of the supply water.
Average output
120 to 200 L per dayMeasured between 8 and 15 °C and at 3 to 5 bar.
Discharged water
3 to 4 L for 1 LDepending on the water quality and the available pressure.
Feed
None, mains pressureNothing to plug in, nothing to programme.

Retention

Dissolved salts
95 to 98%The same range applies to hardness agents.
Bacteria
99 %The best retention of this unit.
Sulphates and aluminium
97 to 98%The cadmium is between 95 and 98%.
Nitrates and silicates
90% at mostOne tenth gets through, which matters with heavily loaded mains water.

Connection and levels

Working pressure
3 to 5 barAccepted range of 2 to 6 bar maximum.
Water temperature
8 to 15 °CRange within which the nominal output is achieved.
First stage
5 µm pre-filterSand, rust and particles, before anything else.
Second and third stages
Activated carbon, then membraneThe carbon protects the membrane, which cannot tolerate chlorine.

To budget for separately

Collection container
A food-grade containerPlaced on the floor beneath the outlet, to fill without holding the pipe.
Remineralisation
Enough to raise conductivityOsmosis water should never be poured straight into a stocked tank.

6 further specifications are available in the detailed view.

In the box

  • 1 fully assembled reverse osmosis unit, with its three stages in place
  • 1 5 µm pre-filter, 1 activated carbon cartridge and 1 membrane, fitted
  • 1 set of pipes and 1 tap fitting
  • 1 flow restrictor and its clamps
  • 1 wall bracket and 1 filter housing key
  • 1 instruction manual

Manufacturer's values recorded on 20/09/2026 from the product page for item 80545. Output depends on the quality of the feed water.

Manufacturer and product safety

Manufacturer
Dohse Aquaristik GmbH & Co. KG
Postal address
Otto-Hahn-Str. 9, 53501 Grafschaft-Gelsdorf, Allemagne

Information provided under Regulation (EU) 2023/988 on general product safety.

Which reverse osmosis unit for what you are preparing?

Three appliances with very different capacities, two of which work without electricity.

Mounted, compact or high-capacity Three ways of getting the same water, which do not require the same space or the same electrical installation.

Maximum output (L/day)Output of the entry-level model (L/day)Salt rejection, at best (%)Water discarded per litre producedWorks without a power socketAutomatic production cut-offBuilt-in water quality monitoringPrice
Compact reverse osmosis unit ARKA myAQUAYour choice400 L/day190 L/day99 %3 to 4 L, 1 to 1.5 L on the 400 versionYesOn the 400 versionOn the 400 version$58.00
Recommended
Dupla RO 200 reverse osmosis unit supplied assembled, no electricity neededYour choice		200 L/day200 L/day98 %3 to 4 LYesNoNo$92.00
ARKA myAQUA 1900 or 3800 high-capacityYour choice3800 L/day1900 L/day99 %1 to 1.5 LNoYesNo$356.00
Compact reverse osmosis unit ARKA myAQUA
Production
Maximum output (L/day)400 L/day
Output of the entry-level model (L/day)190 L/day
Water produced
Salt rejection, at best (%)99 %
Water discarded per litre produced3 to 4 L, 1 to 1.5 L on the 400 version
Installation
Works without a power socketYes
Automatic production cut-offOn the 400 version
Built-in water quality monitoringOn the 400 version
Dupla RO 200 reverse osmosis unit supplied assembled, no electricity neededRecommended
Production
Maximum output (L/day)200 L/day
Output of the entry-level model (L/day)200 L/day
Water produced
Salt rejection, at best (%)98 %
Water discarded per litre produced3 to 4 L
Installation
Works without a power socketYes
Automatic production cut-offNo
Built-in water quality monitoringNo
ARKA myAQUA 1900 or 3800 high-capacity
Production
Maximum output (L/day)3800 L/day
Output of the entry-level model (L/day)1900 L/day
Water produced
Salt rejection, at best (%)99 %
Water discarded per litre produced1 to 1.5 L
Installation
Works without a power socketNo
Automatic production cut-offYes
Built-in water quality monitoringNo

Manufacturer values noted on 20/09/2026 from the ARKA and Dupla product pages, supplemented on 11/10/2026 from the ARKA myAQUA 400 and 3800 pages. The stated output is a maximum, achieved at favourable pressure and temperature.

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Lightweight parcel, dispatched within 48 hours by Colissimo or Chronopost to your home, as you choose at payment. The exact cost depends on the method selected.

Frequently asked questions

10 questions

6 key questions, 10 in the detailed view

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