A reverse osmosis (RO) water filtration system removes undesirable (and along with them healthy minerals) dissolved inorganic solids (e.g. salt, minerals, metals) from water by transferring the water through a semi-permeable membrane.

Even though RO systems remove most of the beneficial minerals, such as calcium and magnesium, along with the undesirable solutes, they are still one of the most effective ways of obtaining clean drinking water, especially if the goal is to get rid of fluoride in the water. Of course, it may be necessary to supplement your diet to account for the minerals stripped from your drinking water.

Chemicals & Dissolved  Solids Which Should Be Removed

Reverse osmosis water filtration systems have a membrane which has pore size of approximately 0.0001 micron. This means that consumer-grade under sink RO systems are able to remove the following important elements from tap water:

  • Chlorine: Chlorine is used to treat water to prevent contamination. In fact it is required by the Environmental Protection Agency (EPA) for tap drinking water, the allowable chlorine levels being up to 4 parts per million. The benefits of chlorinated water do come with side effects (e.g. cancer) and that is why many people choose to have their drinking water filtered for chlorine. Even though it is important to use chlorine to treat water while it is being stored or in transit, it is often recommended that before human consumption the chlorine be filtered out, and the most effective way to do so is through a reverse osmosis system.
  • Lead: Lead can enter drinking water in a variety of ways, the most common being the result of pipe corrosion where the piping material contains lead (even in small amounts). This is especially true where the water acidity level is higher. Houses built before 1986 are more likely to use such pipes, and are more susceptible to lead contamination of drinking water. 
  • Fluoride: Fluoride has been added to the United States drinking water supply since the 1940s in an effort to reduce tooth decay. However, in recent years, opponents are asking whether the small benefit gained from tooth decay prevention is worth the potential damage that this additive could cause by getting into the blood stream, and eventually into the brain. There are other side effects to fluoride including weakening the skeletal system, harmful to both male and female fertility, and negative impact on cognitive abilities. Fluoride is one of the most common chemicals for which RO systems are utilized to remove. It 
  • Arsenic: If the presence of arsenic in the body goes past a certain level it can result in vomiting blood, presence of blood in the urine, cramping, and damage to the major organs within the digesting system.
  • Cadmium: The presence of cadmium in drinking water can result in kidney damage, muscle weakness, and can produce flue-like symptoms.
  • Cyanide: It reduces and eventually eliminates body cells from being able to process oxygen, and results in the elimination of the cells. If cyanide poisoning is left untreated, it can result in death.

Beneficial Minerals That Are Removed by the RO Filtration Process

The process of reverse osmosis, due its nature, removes some beneficial elements from drinking water along with the harmful ones. Depending on the diet of those who drink RO filtered water regularly, it may be necessary to put back some (or all) of the healthy minerals removed by the RO process.

The primary minerals which are removed from water through reverse osmosis, due to their large size molecules include:

  • Magnesium
  • Iron
  • Sodium
  • Calcium

Even though the stripping of water from these (and other) minerals could potentially be problematic, if those consuming RO water have an otherwise balanced diet, there should be no shortage of any of these minerals for a healthy body.

It is recommended that any time a major change takes place in your diet or physical activity that a physician be consulted. Everyone’s body is different and may react differently to food and its environment.

Stages of Reverse Osmosis Water Filtration Systems

Generally, there are 5 primary stages of filtration, with one additional step added by certain RO systems to remove any taste that may result from the storage of the water in the RO storage tank.

Stage 1 – Pre Sediment Filter

This is the first stage of water filtration and is designed to remove larger particles from the contaminated water. This stage removes particles such as dirt, rust (picked up from some water pipes), and variety of sediment.

Stage 2 & 3 – Pre Carbon Filters

These are the activated carbon filters which remove undesirable chemicals such as chlorine, fluoride (not all filters remove this) and other organic chemicals. These two filtration steps are responsible for removing most of the bad taste and smell that may be present in the water being treated.

Stage 4 – RO Membrane

The membrane which have pores small enough to only let through water molecules does a large portion of the water filtration work. The membrane makes it possible to remove most dissolved solids (down to as much as 1/10,000 micron) from the water that is being fed through the reverse osmosis system resulting in the removal or reduction of such dissolved solids as arsenic, lead, copper, some parasitic cysts, and other such contaminants.

Stage 5 – Post Filtration Treatment

The fifth stage of filtration is an additional step which some RO systems have. Even though is is not a requirement, it does result in better tasting water. Since most residential under-sink reverse osmosis systems utilize a balder tank to pump the water out of the faucet at a healthy rate, the holding tank can leave a rubbery taste to the water, and this is what the fifth stage in the RO filtration process removes. This fifth stage utilizes another activated carbon filter to remove the taste.

Parts of a reverse osmosis water filtration system

Benefits of Using a Reverse Osmosis System

Before investing in a reverse osmosis water filtration system, make sure that an RO system is the right fit for you and will provide the types of benefits for which you are looking. Most reverse osmosis water filtration systems provide similar benefits which include:

  1. Better Tasting Water: Since RO systems remove a large variety of chemicals and dissolved solids, water treated by RO systems will taste better compared to that straight out of the tap (in most situations).
  2. Reduced Chemicals: RO systems remove a large portion of undesirable chemicals and minerals including lead, fluoride, arsenic, rust, and chlorine.
  3. Low Maintenance: RO water filtration systems are low maintenance, as they require only filters to be changed once every 6-24 months, depending on frequency of use, quality of water, and type of filter.
  4. Efficient: Even though there is some water wasted through the filtration process, RO systems are highly efficient in producing high quality water.
  5. Affordable: With an initial investment of between $100-$300, and relatively inexpensive filters, the cost of having good quality water can be affordable for almost any budget.

Reverse Osmosis Filtration System Maintenance

Revers osmosis water filtration systems are easy to maintain, as they do not require frequent cleaning and filter changes.

Consult your RO system manufacturers recommended schedule for cleaning and filter changes. The below is a general guideline of what is required.

Filter Changes

  • Sediment Filter: Replace every 12 months. This portion of the RO system does the initial heavy lifting, so maintaining a consistent change schedule is important.
  • Carbon Filter(s): Replace every 12 months. Responsible for removing chemicals such as chlorine, having a consistently replaced carbon filter will result in better-tasting water.
  • Revers Osmosis Membrane: Replace 2-3 years. If the preceding filters are replaced on the schedule recommended by the manufacturer the semi-permeable membrane of the RO filter will only need to be changed every 2-3 years.
  • Polishing Filter: Replace every 12 months. The final filter which removes the rubbery taste from the holding tank is an important final stage, and can impact the performance of the system if not changed based on the recommended schedule.

RO water filter change schedule

Reverse Osmosis Waste Water

Reverse osmosis systems by the nature of the way they function produce waste water. The amount of waste-water produced as a result of the RO filtration process varies based the water pressure of your municipal water system. The higher the pressure the less waste water the system will produce. Water temperature can also impact the amount of waste-water produced by an RO system—the colder the water the more water is wasted.

All conditions being perfect an RO system will produce one gallon of waste-water for every gallon of filtered water. The amount of waste-water can be as high as four gallons per every gallon of filtered water.

Recommended Reverse Osmosis Water Filtration Systems

iSpring RCC7AK 6-Stage Superb Taste High Capacity Under Under Sink Reverse Osmosis Drinking Water...
  • High Capacity Reverse Osmosis water filtration for safer, healthier water. This under sink mounted water filter and water softener removes up to 99% of over 1, 000 contaminants, including lead (removes up to 98% of lead), chlorine, fluoride, arsenic, hormones, asbestos, calcium, sodium, bacteria, giardia, viruses and more.
  • Experience clean, safe, good-tasting water every time you turn on the faucet. Enjoy crystal clear ice cubes, fresher tea and coffee, better tasting foods, healthier baby formula - even better than most bottled water.
  • The RO membrane removes not only harmful pollutants but also a few helpful minerals. As a result, a standard 5 stage RO system produces slightly acidic water with a pH of 7. 0 or below. The iSpring RCC7AK includes an additional sixth stage - an Alkaline Remineralization filter which restores healthy minerals and produces a balanced alkalinity, which gives the water a more natural taste than regular 5 stage RO water.
  • Premium quality components ensure highest reliability and low maintenance for many years to come. Clear see-through 1st stage housing makes filter inspection a snap.
  • Easy, do-it-yourself installation, typically in a couple of hours with industry-leading help just a phone call away. Fits under a standard kitchen sink, with all parts included and clear, well-organized instructions and videos. For leak-free installation, simply push tubing ½ inch deep into quick-fitting connectors and lock - no threading pipes needed.
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APEC Top Tier 5-Stage Ultra Safe Reverse Osmosis Drinking Water Filter System (ESSENCE ROES-50)
  • Supreme quality - designed, engineered, and assembled in USA to guarantee water safety & your health.
  • Only technology to remove up to 99% of contaminants including arsenic, chlorine, lead, fluoride, heavy metals, bacteria, virus and 1000+ contaminants. System Capacity- 50 gallons per day @ 60 psi, 30 gallons/day @50 psi and 77 deg F.Tank Capacity-4 gallons. Feed Water pH- 2.0 -11.0. Max Total Dissolved Solids- 2000 ppm. Feed Water Pressure 40-85 psi.
  • Premium long-lasting filters used to treat tap water, well water. Provide unlimited clean, refreshing crisp tasting water superior to bottled water
  • America's No.1 rated water filter brand with 20 years of success guaranteeing trouble free, noise-free system for long lasting, dependable, pure drinking water.
  • System comes with 100% lead-free designer faucet, plus FDA Certified JG Food grade tubing and parts to provide safe, contamination-free pure water..Pipe Size:1/4 inches
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APEC Top Tier Alkaline Mineral pH+ 75 GPD 6-Stage Ultra Safe Reverse Osmosis Drinking Water Filter...
  • Supreme quality - designed, engineered and assembled in USA to guarantee water safety & your health.
  • 75 GPD 6-stage system removes up to 99% of bacteria, viruses, cysts, organics, chemicals & more. Feed Water Pressure: 40-85 psi.
  • US made cartridge uses food-grade calcium from trusted source for safe, proven water pH enhancement. Enjoy ultra-pure drinking water with added calcium minerals for improved ALKALINITY and great taste.
  • Premium long lasting filters used to treat tap/well water. Provide unlimited clean drinking water.
  • America's No.1 rated water filter brand with 20 years of success guaranteeing trouble free, noise-free system for long lasting, dependable, pure drinking water.

Last update on 2019-06-15 / Affiliate links / Images from Amazon Product Advertising API