Effectiveness of Water Filters for Reverse Osmosis

Water filters for reverse osmosis consist of two components, a pre-filter and a semi permeable membrane. The pre-filter you select for your system will depend on the contaminants present in your water supply. If you have heavy sediment or use a private residential well, you will want a sediment filter before the semi permeable membrane. Carbon filters are also used in many filtering units.

Residential reverse osmosis systems use a semi permeable membrane in the reverse osmosis process, regardless of the pre-filter used. This membrane is porous and removes about 99% of most pollutants and microorganisms. A cross flow system uses wastewater to flush contaminants down the drain with the wastewater. This method keeps the membrane clean and capable of filtering water effectively. The semi permeable membrane will need to be changed between two and four months, depending on the amount of use.

Carbon filters use charcoal as the media for filtering water prior to the reverse osmosis process. These are the most commonly used filters for residential use. They are effective at removing dangerous bacteria, such as giarida and cryptospordium. These bacteria have been found in both private wells and municipal supplies across the country and are known sources of water borne illness. In addition, a system employing carbon filters remove lead, chlorine and other dangerous chemicals used to treat municipal sources.

Sediment whole house water filters are generally recommended for a residence that uses a private well. They are effective at removing sediment, keeping the semi permeable membrane cleaner. The filter size you need depends on the amount of sediment in your water. You will need to change this filter often, depending on the amount of sediment removed. In most homes using one of these with a reverse osmosis system, the sediment filter will need to be changed about once a month. Water with extremely heavy sediment levels may need more frequent changes.

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