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What is Reverse Osmosis ?



Reverse Osmosis is a filtration method that removes many types of large molecules from solutions by applying pressure to the solution when it is on one side of a membrane.   Basically, water is forced under pressure thru a membrane, typically a Thin Film Composite ( TFC ) membrane. This membrane will not allow larger molecules of contaminents to pass thru, but will allow pure water molecules to pass thru.


      Reverse Osmosis is a common filtration system used for purifying drinking water in residential applications.   Reverse Osmosis ( R.O. ) drinking water systems typically consist of one or two pre filters, used to protect the membrane and most importantly to remove the chlorine for TFC membranes.  Thin Film Composite membranes do not last long if the residual chlorine is not removed first.  R.O. systems usually have a post filter, typically an activated carbon filter, which is used to " polish " the taste of the R.O. water, giving the drinking water a pleasant drinkability.  And of course an R.O. system will have a membrane.  The membrane is what is removing the contaminents from the water, typically 90% to 96%  This high removal percentage of contaminents means the drinking water is almost completely purified, nearly completely free from most all harmful impurities.  An R.O. system will also have a holding tank to store the water, as the actual process of purifying the water is a relatively slow process.  A good R.O. system can produce roughly a gallon of water an hour.


The Process of an R.O. System :  


      Most R.O. systems are installed under the kitchen sink, and have a specific faucet for the purified drinking water.  The process of an R.O. system is usually like this : The R.O. system has a water feed line, which is connected from the cold water supply line to the regular kitchen sink faucet.  The feed water line directs water into the R.O. system, and into the pre filter ( sometimes two pre filters ).  Then the water enters the membrane. This is where the impurities are seperated from the pure water.  The impurities are rejected, and directed to the sink drain. The pure water molecules are able to pass thru the membrane, and are then directed to the holding tank, where it is stored for future use. Once the holding tank is full, the system will automatically shut off.  When water is needed at the at the R.O. Faucet, the pressure in the holding tank pushes the water back out, thru the final post carbon filter, and then up to the faucet. With most R.O. systems, another water line can be ran from the R.O. product water to the fridge. This allows the same purified water to be directed to both the R.O. faucet at the sink and the fridge / ice maker.