Tankless Reverse Osmosis System, replacement filter once a year – Waterdrop
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Tankless Reverse Osmosis System with small size, replacement filter once a year - Waterdrop D4

  • Easy Installation, Intelligent Filter System, Brushed Nickel Faucet


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Key Feature

  • Revolutionary filter structure: The innovative technology and design to integrate 6 different filter materials into one composite filter are adopted, making the reverse osmosis system more compact and achieving the best filtering effect. It can reduce 1000+ harmful substances and protect the safety of drinking water for the whole family.
  • 1:1 drain ratio, 300% more filtered water than traditional RO machines, efficient use of water resources and saving water bills.
  • Great upgrade with small size: The elegant tankless reverse osmosis system is only 12.44-inch in height. The tankless design makes its size even smaller, which helps save more space under the sink.
  • Stylish faucet with metal finish: The RO water filter system comes with a stylish faucet with a metal finish, providing you a fast and extensive flow.
  • Safer & cleaner: The integral waterway design eliminates connectors in the internal water tubing, which lowers the risks of water leakage and bacteria growth.
  • Effortless replacement: Waterdrop reverse osmosis water filtration system only requires replacement once a year, and you can complete the replacement by opening the front panel and removing the old filter.

Tankless Reverse Osmosis System with small size, replacement filter once a year - Waterdrop D4

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Tankless Reverse Osmosis System with small size, replacement filter once a year - Waterdrop D4

Model number
Product dimensions
16.02 x 6.22 x 12.44 inches
Rated voltage/ Frequency
110-120V/ 60HZ
Rated power
Service flow rate
0.28 gal/min
Feed water pressure
14.5-87 psi
Feed water requirement
Municipal tap water
You need to know your water source and water quality at first.
The key to find a suitable water filter for yourself is to know your local water quality. Most RV sources water from municipal tap water. City water suppliers use chlorine to disinfect municipal water and eliminate waterborne-disease carrying bacteria. However, chlorine can leave water with a chemical taste and smell.
Regardless of the water's source, if you are in a region of the country with hard water, your RV will be exposed to high levels of calcium and magnesium, which can lead to scale build-up and damaged plumbing.
Waterdrop D4 Reverse Osmosis Water Filtration System effectively reduces chlorine, sediments, heavy metals, bacteria, chemicals, viruses and more, basically any impurities larger than 0.0001 micron. That means this filter can also reduce TDS and soften your water sources. This system is one of the best water filter for your RV.
Also in some RV parks, they use local well water as source. Well water can possess high levels of sediment, heavy metals, and potentially bacteria and microorganisms. If so, we suggest you to install a pre-filter, blocking out large particles initially. Pre-filtered water without large particles travels into RV can protect water-related appliances in your RV.

How does reverse osmosis system work?

The water supply in your home gets in under pressure, irrespective of where you live. Reverse osmosis relies on this same pressure to push water through a semipermeable membrane.
Water passes through the semipermeable membrane under pressure. This leads to the separation of the impurities from the water molecules. The impurities are on one side of the membrane, and the water molecules on the other, with the clean water going to your tap without any impurity whatsoever. There are several filtration stages in the RO water filtration process - up to seven sometimes, and these are responsible for the high purity of water.

What are the advantages of Waterdrop reverse osmosis systems?

When you buy the Waterdrop D4 reverse osmosis water filtration system, you are meeting the need for pure water in your household while adding to the beauty of your interior. The artistically designed housing houses an innovative technology that delivers an excellent filtration performance by combining multiple filtration materials into a single composite filter.
You only need limited space to install this tankless reverse osmosis system. Its optimized filtration performance means it reduces heavy metals, chlorine, and even TDS. This system packs a powerful filtration performance and an ultra-extended service life despite having a single composite filter.
With just one filter replacement all year long, this Waterdrop reverse osmosis water filter will serve you with maximum convenience.

Can I drink reverse osmosis water everyday?

Yes, it is perfectly safe to drink reverse osmosis water frequently. There are fewer contaminants in the water, so you are safe. The absence of contaminants means you are not prone to health issues like brain damage or anemic conditions in children. Parasites causing diseases are also eliminated from your water sources, providing you with clean and pure water.

What is the flow rate of this reverse osmosis water filtration system?

This Waterdrop reverse osmosis system can deliver 0.28 gallons of water in a minute, conveniently meeting your household water needs.

Does Waterdrop whole house reverse osmosis waste a lot of water?

For a traditional RO system, wastewater production is inevitable. However, the Waterdrop D4 RO purifier is powered by advanced technology that keeps the drain ratio at 1:1. Therefore, you can save up to 300% more water than the tanked traditional filter systems. You also spend less on water bills.

How to install the reverse osmosis home system?

The simple design ensures an easy installation. You can be done in less than 30 minutes without needing any external help. All you have to do is check the instruction manual, and if you encounter any problem, watch the installation video on YouTube.

How long does a reverse osmosis filter last?

The integrated filter in this system needs to be replaced once every year.

When to replace the filters of this reverse osmosis system?

You should replace it only once a year, depending on the quality of your local water.

Can I connect a water softener with this reverse osmosis system?

a. Please note that the water softener is NOT designed to provide drinkable water. Its main function is to soften the water for washing clothes, taking a bath, flushing toilets, etc.

b. If a salt-based water softener is installed BEFORE the RO unit:
-The filtered water could be salty since our unit can only remove 90% salt added by the softener.
-The RO filter's lifetime could be shortened due to the unusual amount of sodium in the source water, which is NOT covered by the warranty.
-We have already put a clear warning on the product page regarding this aspect.

c. If your water softener is NOT salt-based, then our RO unit should work properly with it.

Can I use this reverse osmosis system in my RV?

Yes, this reverse osmosis water filtration system can work with your RV. It has an integrated design that makes it possible to install it even in a tiny under-sink space, such as RVs. You can combine this filter system with your RV for a regular and reliable supply of clean water.
Now you can stop using the dirty and unsafe water from campgrounds. This filter system ensures you get clean and pure water for drinking directly from your taps and shower. You are also immune to the common health issues associated with contaminated water, which may prevent you from enjoying your road trip.

Is this reverse osmosis water filtration system suitable for well water?

We do not recommend using well water as source for our RO systems.
The reasons are as follows:
1. Large particles.
Compared to municipal tap water, the well water is rich of large particles, which will clog the filters easily, and shorten their lifetime significantly.Please note that the filters will still need to be replaced more frequently, even if you have added a pre-filtration system.
2. Composition
The well water has very complicated compostion, and some of them (apart from the large particles) can cause the filter or internal valve to be clogged and prevent the RO system from normal performance.
3. Water pressure
The well water may not provide the feed water pressure that the RO system requires (14.5 psi min.). Furthermore, the water pressure will be even lower after passing through pre-filtration systems.

Do I need to have an electrical outlet under my sink for this work?

Yes, the system requires electricity to work. So, an electrical outlet is necessary.

Can I connect the remineralization filter with this reverse osmosis water filter?

Yes, this reverse osmosis water filter works perfectly with a remineralization filter. All you have to do is buy a suitable remineralization filter and connect it to the system. Simply search for “Waterdrop Remineralization Filter” and add the filter.

What does Pure to Drain Rate mean?

The reverse osmosis water filter relies on a semi-permeable membrane to filter out impurities from drinking water. When the tap water is compressed through the RO membrane, it produced pure water and waste water. The ratio of pure water to waste water is called wastewater ratio. 1:1 wastewater ratio means 1 gallon water is wasted per 1 gallon purified, and 2:1 wastewater ratio means 1 gallon water is wasted per 2 gallon purified. The higher the wastewater ratio is, the less waster water produced during the filtration process. During the use of RO water filter, the actual ratio might be lower than the labeled, depending on many factors such as water quality, pH, pressure and temperature.
Upgraded 6 Stages Filtration
Upgraded 6 Stages Filtration
6-in-1 filter, filter layer by layer, the filtration accuracy is only 0.0001μm. Reduce 1000+ harmful substances in water to ensure the health of drinking water for you and your family.
Filtered Water Increased By 300%
1:1 drain ratio, compared with the traditional RO machines, it can filter up to 300% more purified water, make efficient use of water resources, and save your water bills
Filtered Water Increased By 300%
Quick Replacement, Convenient Life
Quick Replacement, Convenient Life
The intimate buzzer reminds you to replace the filter, you only need to replace it once a year with a push-and-pull, which you can easily operate it at home.
*We do not recommend using well water as source for our RO systems. We do not recommend directly connecting tankless RO to a refrigerator or ice maker. You can connect the RO system to the refrigerator or ice maker with Waterdrop PMT small water pressure tank >.
Fast, Stable, Long-Lasting With 400 GPD
The water output is more rapid, stable and durable. It only takes 12 sec to fill glass of water, which can meet the water needs of the whole household.
Fast, Stable, Long-Lasting With 400 GPD
Compact Design, Save More Undersink Space
Compact Design, Save More Undersink Space
With the composite filter and compact design, the height of this reverse osmosis system is only 12.44-inch, saving more undersink space.
Perfect For Small Spaces
  • Exquisite body, suitable for small spaces, can also be used in RVs without worry, enjoy pure water with our RO water filter system everywhere.
  • Perfect For Small Spaces
    No Noise, Quieter Life
    No Noise, Quieter Life
    Quieter than a laptop when working. You can barely hear no noise closing the door. Rest assured to enjoy a peaceful life.
    No Leaking Risk
    Advanced integral water way with no leaking points. This tankless reverse osmosis system keeps you away from safety risks and protect your family always.
    No Leaking Risk
    Cleaner Filter, More Intelligent
    Cleaner Filter, More Intelligent
    Automatic flushing of filter and water lines. Even if you go out for a short period of 24 hours, you can drink fresh and purified water at home, bringing you pure enjoyment at any time.

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    Need Installation
    Beneficial Minerals × × × × ×
    Flow Rate 400 GPD 600 GPD 800 GPD 400 GPD 600 GPD 400 GPD
    Pure to Drain Rate
    Drain ratio stands for the ratio of wastewater and purified water dispensed by a RO system. For example, the 3:1 drain ratio means it uses up a gallon of wastewater for every 3 gallons of pure water you get.
    Pure to Drain Rate Pure to Drain Rate Pure to Drain Rate Pure to Drain Rate Pure to Drain Rate Pure to Drain Rate
    Faucet Ordinary faucet Smart faucet Smart faucet Smart faucet Ordinary faucet Ordinary faucet
    Display Filter lifespan Filter lifespan & TDS Filter lifespan & TDS Filter lifespan & TDS Filter lifespan Filter lifespan
    Self-clean × ×
    Holiday mode × × ×
    Electricity Required
    Filter Cartridges WD-D4RF







    Noise(≤) 55dB 55dB 65dB 65dB 55dB 55dB
    Filter Lifespan 12 Mths 12 Mths CF-6 Mths
    CB-12 Mths
    RO-24 Mths
    CF-6 Mths
    CB-12 Mths
    RO-24 Mths
    CF-12 Mths
    P6MRO-24 Mths
    MNR-12 Mths
    CF-12 Mths
    MRO-24 Mths
    Dimensions(inch) 16.02*6.22*12.44 15.98*5.98*11.97 18.11*5.67*17.72 18.11*5.67*17.72 17.32*5.91*13.9 17.32*5.91*13.9
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