Reverse Osmosis: What is it and Which Product is the Best?

Reverse osmosis is a water filtration process that improves the appearance, odor, and taste of drinking water. These filters use a semipermeable membrane to remove contaminants such as particles, molecules, and ions, and are considered the top filtration option. They offer a lasting, healthier alternative to faucet and pitcher water filters, and are more economical than buying bottled water.

But how long have we been using reverse osmosis? What is it really? And which reverse osmosis product is the best?

A Brief Overview of Reverse Osmosis in History

In the mid-1970s, FilmTec Corp. pioneered the use of reverse osmosis filters. Having studied seabird, it was discovered that they have a special membrane in their throats. This membrane desalinates the seawater, allowing these birds to drink pure water. FilmTec Corp’s scientists developed a polyamide composite membrane, which was used in a similar manner – to desalinate water.

Since then, the filtration process – which became known as reverse osmosis – has been introduced into a number of different fields, including the pharmaceutical industry. More importantly, it’s been used in homes for the past several decades.

How Does Reverse Osmosis Work?

Reverse osmosis water filters use a built-in high-pressure pump to generate enough force to counter the natural osmosis process. This reverses the flow of pure water toward contaminated water so that the water with impurities is pushed through the membrane instead.

The contaminate water is known as “feed water” in the reverse osmosis process, while the desalinated, filtered water is called “RO water” or “permeate” water.

Contrary to popular belief, the semi-permeable membrane is not the only filtration step in reverse osmosis. In fact, there are typically four (sometimes as many as ten) filter stages in a reverse osmosis system.

The Basic Four-Stage Filter Process

First, feed water is put through the sediment pre-filter. Here, sediment, silt, and dirt is filtered out. This is a crucial first step, as this sediment filter protects the more delicate semi-permeable membrane from the larger particles that can damage it.

Next, feed water passes through a carbon pre-filter to remove chemical and organic contaminants. Similar to the sediment pre-filter, this carbon filter helps to protect the semi-permeable membrane from damage. Chlorine, fluoride, and other chemicals can eat away at the membrane, which would render the reverse osmosis system ineffective. Hard water can also be an issue, which is why it’s typically recommended that you use a water softener in conjunction with reverse osmosis. This carbon filter also helps to vastly improve the taste and odor of your water.

The third step is the semi-permeable membrane. Water molecules are allowed to pass through unhindered, fitting into the membrane’s matrix and forming hydrogen bonds. Soluble salts, pyrogens, bacteria, and any organics that have not been removed by the carbon pre-filter are trapped behind.

In a three-stage reverse osmosis system, the process ends there. But in four-stage systems, there’s a final step: the polishing post-filter. Once the feed water has passed through the semi-permeable membrane, it is put through a second carbon filter before leaving the system. This makes sure that any lingering odors or tastes are properly removed.

Depending on the reverse osmosis filter model, the system removes 90% to 99% of all water contaminants.

The Basic Components

The filters aren’t the only components that make up a reverse osmosis system, of course. There are actually several different working parts. Below is a brief overview of the basic components of a 4-stage point-of-use reverse osmosis system. For a more in-depth look at these parts, take a look at the following article.

  1. The cold water line valve.
  2. Sediment pre-filter.
  3. Carbon pre-filter.
  4. Semi-permeable reverse osmosis membrane.
  5. Pressurized water storage tank (typically 2 to 4 gallons).
  6. Carbon post-filter.
  7. Automatic shut-off valve to prevent water wastage.
  8. Check valve (located in the outles section of the membrane housing).
  9. Flow restrictor (this regulate the flow of feed water through the membrane) – most often found in the RO drain line.
  10. Reverse osmosis faucet (typically installed on the sink faucet) – some models use a non-air gap model, while residential plumbing restrictions may require an air gap faucet.
  11. The drain line, which runs from the membrane housing outlet to the drain (this is used to dispose of the waste water and contaminants).

Best Reverse Osmosis Water Filter Review

Home Master TMHP HydroPerfection Under Sink RO System


Our top recommendation for a reverse osmosis water filter is the Home Master TMHP, a fully featured system. The TMHP HydroPerfection includes a permeate pump, which allows for a 75-gallon daily output while reducing the amount of water required for flushing the membrane. This produces a 1:1 water waste ratio, meaning that for every gallon of RO water only one gallon is used for flushing.

Another fantastic feature is the UV light filter, which is the final step of this impressive 9-stage reverse osmosis system. The Home Master TMHP also uses a remineralization filter to add minerals back into the RO water, after which the UV light kills 99.8% of any additional microorganisms. This also reduces acidity by balancing the pH levels, acting similarly to an alkaline filter.

The Home Mster TMHP also comes with an upgraded faucet and permeate pump. Additionally, it also has a larger 3/8-inch tubing, which increases the flow rate. Maintenance is remarkably easy, requiring only that you replace the filters once every 12 months (or after 2,000 gallons). No tools are necessary for this process – simply pull out the old and push in the new!



Final Words

Although the Home Master TMHP is more expensive than many other point-of-use reverse osmosis systems, it must be remembered that it isn’t a mere four-stage filter but an impressive nine-stage model. This also makes it suitable for both municipal and private well water.

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