What is a Reverse Osmosis water filter system?

Aug 16, 2019

What is Reverse Osmosis filtration and how does it work?

Reverse Osmosis is a water filtration process that removes ions, unwanted molecules and large particles from drinking water, using a semi-permeable membrane. The main principle is that the water is being pushed through a membrane that is so fine, that only water (H₂O) molecules can go through it. It is important that the water that is being pushed is mostly free of sediments, as the membrane can get clogged.

Reverse Osmosis filtration flushes around 50% of the water that is pushed through. If 1000 litres of water passes through the membrane, you will only get about 500 litres of usable water. The rest of the water, also known as brine (containing pollutants), is evacuated and pushed into the sewage/grey water system. To increase the lifetime of the RO membrane and maintain a good throughput, the water should go through sediment filters before it reaches the RO stage.

Reverse Osmosis can remove various types of chemical compounds as well as biological ones (mainly bacteria) from water, and is used both in industrial processes and the production of potable water. Click here to see Recommended Reverse Osmosis Water Filters.

What are the benefits of Reverse Osmosis water filter systems?

  • Powerful & efficient filtration system
  • Easy to maintain & cost-effective
  • Provides better quality & tasting water
  • Removes common chemical compounds (metal ions & aqueous salts) including: sodium, copper, chloride, chromium, & lead
  • Removes or strongly reduces arsenic, radium, fluoride, magnesium, sulfate, potassium, calcium, nitrate & phosphorous

How do you install a Reverse Osmosis water filter system?

Domestic RO water filter systems can be installed under the counter and are typically used to filter the water of one tap.

A typical system includes several stages:

  • Sediment pre-filters
  • Carbon pre-filter to remove chlorine & some pollutants
  • RO membrane
  • Inline GAC  /carbon / mineral filter to add some minerals back, fix the pH or improve the taste of water

Reverse Osmosis systems generally include a pressure tank of 5-10 litres as the flow of water is very limited. The system pushes the water into the pressure tank continuously until it is full. When the tap is opened, the water comes directly from the pressure tank.

If the water supply feeding the RO system has a pressure below 3 bars (300kPA), it is recommended to add a pressure booster pump to the system.

Larger RO systems rated at 800 GPD (Gallons per Day, 1 Gallon = 3.8L) can be used to supply an entire house, but always with a fresh water storage tank. RO systems rated at 1600 GPD and higher are recommended for commercial use (restaurants, food industry, etc).

What are the costs of Reverse Osmosis water filter systems in South Africa?

Costs vary between R1500 and R5000 for a domestic, undercounter RO filtration system rated at 50 or 100 GPD. If you intend to filter water for the entire house, costs will range between R20000 and R30000. To filter borehole water or for commercial use, systems costs typically exceed R20000 depending on volume and quality of the local water supply.

Those prices are from 2019 in South Africa.

How do you maintain a Reverse Osmosis water filter system?

Reverse Osmosis pre- and post-filters should be replaced every 6 months to 1 year, and membranes every 2 to 4 years.

Recommended Reverse Osmosis Water Filters

Reverse Osmosis Water Filter System 75GPD With Pump (280 Litres Per Day) 10 Inch
Reverse Osmosis Water Filter System 75GPD With Pump (280 Litres Per Day) 10 Inch
Reverse Osmosis Water Filter System 75GPD Without Pump (280 Litres Per Day) 10 Inch
Reverse Osmosis Water Filter System 75GPD Without Pump (280 Litres Per Day) 10 Inch

Are Reverse Osmosis water filter systems recommended when purifying water?

We recommend using a Reverse Osmosis water filter system if you reside in an area where municipal water is polluted by something else other than bacteria; in areas where agriculture is intensive; and in mining areas. It is also recommended for borehole or wellpoint water. Compared to a Big Blue with UV filtration system that focuses on sediments, chlorine, bacteria and germs, Reverse Osmosis is more geared towards the removal of heavy metals and pollutants from your drinking water.

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