If you live in an area where the local water contains various contaminants or unwanted additives -- or you're just turned off by the strange taste of tap water -- a reverse osmosis water filter system could change your life, or at least how you consume water at home. RO for short, reverse osmosis water filter systems are like sanitizing filters for your tap water, no matter your water source

What is reverse osmosis?

Simply put, reverse osmosis is a process to remove contaminants in water. It works by pressurizing and running your existing water through various filters and a semipermeable membrane, which sends water through and out the other end, yielding permeate, or clean drinking water.
The byproduct of reverse osmosis is brine, or the concentrated leftovers from the RO process. To help filter the water, the semipermeable membrane itself has small holes that block contaminants but not H2O, and the pressure is what sweeps the remnants away, sending clean drinking water out the tap.Learn more about reverse osmosis pressure tank.

What are the stages in a reverse osmosis system?

In an RO system, water is first sent through a prefilter to remove sediment and chlorine, among other things, then through the semipermeable membrane to remove any dissolved solids. After the membrane, a postfilter cleans the water further before it is delivered to the faucet for drinking. Some systems have more or less filters and different stages of water filtration, but all RO systems follow this typical design with a membrane and filters before and after.
The more stages of the filtration system, the thorougher of the filtered water. After passing through the prefilter to remove the large sediments in water, the second stage normally would be an activated carbon filter to further remove large particles, and more importantly, the chlorine in water, which could damage the RO membrane.
Then the water will pass the third stage to a semipermeable membrane, also known as the RO membrane. The RO membrane contains tiny pores with a size of 0.0001 micron and removes the following elements that could be present in drinking water: lead, copper, barium, chromium, mercury, fluoride, nitrite, nitrate and selenium.
The water is normally safe to drink after the RO membrane, yet, most of the systems would have a post activated carbon filter to improve the taste. Nowadays, many systems offer a remineralization feature to add back beneficial minerals as well as UV sterilizer to kill the bacteria within the filtered water tank. The UV feature would not be necessary if your system is tankless.

Factors you need to consider when choosing a RO system

Source water

Before diving into the marketing research and comparing all types of water filtration systems, you first need to understand your source water. There are mainly two types of source water in the US: municipal water and well water.
If you are living in urban areas, then your source water most likely comes from a nearby water treatment plant. Municipal water has been treated before pumping into homes, meaning less impurities and contaminants.
For people who live in suburban areas, the private wells are usually the main source of water. The well water normally contains higher amounts of living microorganisms, viruses, and bacteria.
The source water type indicates the requirements of the level of filtration accuracy.

Source water

One of the common overlooked aspects of choosing the best reverse osmosis water filtration system is its efficiency. The water flow rate is one significant factor that you should learn before purchasing a reverse osmosis system. Many consumers complain about waiting 4 minutes for a glass of water. Make sure you find out how quickly these systems you’re considering operate.
Besides that, the majority of the reverse osmosis systems come with a finite number of gallons they can handle in a day. Across the market, you’ll find those that can handle between 50 and 100 gallons. Yet, some of the advanced systems can handle over 400 gallons per day. If you only have a few people in the house, the smaller size may work for you, otherwise, you may want to opt for the larger capacity. Thus, checking on both the water flow rate per minute as well as the average filtered water per day would be helpful.


Many people are reluctant to install a whole house reverse osmosis system for the waste water concern. There are systems out there that will discard more waste water than the actually filtered water. Thus, reading through the specs and finding out how much water is filtered off in general is necessary.
The ideal ratio of waste water vs purified water is 1:1, which should be the benchmark when comparing different systems on the market.


Plumbing service could be very costful, and most people would not relish the idea of tearing the sinks apart to integrate a complicated reverse osmosis water filtration system. When researching the systems on the market, you are highly recommended to check the system installation and make sure the installation is simple and easy-to-follow. The technical complications should not prevent people from accessing clean water, not to mention the additional cost to the system itself. Find a system that offers easy DIY installation within an hour!

Available space

Depending on the kitchen under sink space, you need to make sure the system can be fitted into and not taking the whole space. Generally saying, the majority of the filtration systems on the market come with a storage tank as these systems filter water quite slowly, and a pressured water tank helps provide clean water faster. This is also the most commonly used design in early evolution of the water filter systems.
As people’s living standard improves, the manufacturers of the water filtration system have upgraded their design and launched systems with high filtration speed and no tank. Consumers can enjoy safe and clean drinking water fresh from the tap without waiting. The tankless design saves much undersink space, and more importantly, it eliminates the risks of secondary pollution within the water tank.

The best reverse osmosis water filter system

Here at Waterdrop, we believe there's a better way to do reverse osmosis. Instead of bulky tanks and unsightly filters that clutter up the area under your sink, Waterdrop's no-tank design yields a surprisingly minimal system that sits under 18 inches tall and less than six inches wide. That's a fraction of traditional RO systems, which are 50 percent larger and bulkier with awkward filters and tubing left out in the open for you and your family to inadvertently snag.
A Waterdrop RO system is also much more robust than a typical RO system, giving you a full glass of water in just 12 seconds with a flow of 400 GPD, or 0.28 gallons a minute. That's compared to traditional RO systems that manage only a 50 GPD or 0.03 gallons a minute. Our faucet is also an engineering marvel, adding a touch of modern elegance to just about any water source in your home, and the smart, glowing base even tells you when it's time to replace a filter or service your system.

Benefits of drinking RO water

Protection from Chemicals

This should be listed as the most important of the benefits of RO water as it removes harmful chemical agents from the water before you drink it. Water that comes from the tap in your sink is treated at the local water plant to some degree, however, this water travels through the city’s plumbing grid and then through your own pipes before it gets to your tap. If there are any impurities in that system of pipes, which is likely the case, they could wind up in what you drink. Examples of substances found in tap water by way of various studies over the years include:
  • Arsenic
  • Aluminum
  • Lead
  • Chlorine
  • Radium
  • Potassium
  • Nitrate
  • Phosphorous

Environmental friendly option

If you’re thinking that bottled water is the answer, you may want to revisit that idea. Ignoring the environmental damage that these bottles inflict on the planet and even putting aside the WHO story from above, Food & Water Watch published a report stating that approximately half of all bottled water actually comes from the tap. You need to keep these harmful substances out of your system.