Reverse osmosis (RO) is a water purification process in which water is forced through a semi-permeable membrane that removes 90-99% of tap water impurities. The result is water that is free of minerals and other contaminants. Membrane type determines the amount of dissolved solids a unit is capable of removing. For example, Cellulose Tri-Acetate (CTA) membranes have a removal rate of 88-94%, Thin Film Composite (TFC) membranes remove between 94-98% of dissolved solids, and Hi-S Membranes have higher removal rates, between 97.5-99%, and are especially adept at removing silicates.

More ' What is reverse Osmosis ? '
 

Tap water often contains impurities that can cause problems when added to an aquarium. These include phosphate, nitrate, chlorine, and various heavy metals. High levels of phosphate and nitrate fuel aggressive algae growth, and copper, often present in tap water due to leaching from pipes, is highly toxic to invertebrates. Because RO filters remove practically all of these impurities, they are becoming more popular among aquarists, particularly marine hobbyists.

Reverse osmosis and deionization (DI) perform the same task of removing impurities from tap water. However, DI purifies water utilizing the principle of ion exchange to remove impurities and replaces them with pure water. In most instances, an RO unit serves as a well-rounded filtration method that removes the majority of impurities; coupled with a post deionization filter, the resulting water is 99.9% pure. Many RO units are available as a combined RO/DI unit or are able to accommodate an add-on DI unit that simply attaches to your existing RO unit.

If your RO product water is pure, your aquarium should have minimal algae growth, a steady pH level, and low phosphate and nitrate levels. You can check the purity of your RO product water using a conductivity meter, TDS meter, or by measuring the general hardness and alkalinity of the water with a test kit. Purified water will have a general hardness of 0 GH and alkalinity of 0 dKH. If your test values vary from those described above, you may need to replace cartridges and/or the RO membrane.
 

It's not likely that you received a defective unit. But there are a few factors that effect the output of reverse osmosis units. These factors include; the source water pressure, temperature, and the amount of total dissolved solids within the source water.

The ideal operating pressure for a RO (reverse osmosis) unit is 65 psi (pounds per square inch). An operating pressure of 45 psi will reduce the output of a unit by 50%. There are pressure gauges available to monitor the operating pressure of the system. If the operating pressure is too low, an RO pressure boosting pump can be added to increase the operating pressure to the ideal range. (click here for more information about our SuperPump).

The temperature of the source water should ideally be in the 70° to 77°F range for optimal performance. A temperature of 50°F, or lower, will reduce the output of the unit by 50% or more. Either hot or a mix of hot/cold tap water should never be used for the source water due to the minerals that are added to the water from most water heaters.

Finally, the amount of total dissolved solids in the source water can reduce the amount of water produced by a RO unit. The PurePro units are rated to treat water with a dissolved solid amount of 500 ppm or less. If your source water contains a higher concentration, it would be wise to install a mechanical pre-filter in line prior to the unit. These filters are available at most hardware stores. Because of the requirements of reverse osmosis units, it is wise to purchase a unit that is rated above the gallons per day that your needs require.

Reverse osmosis (RO) systems remove most of the impurities (heavy metals, minerals, nitrates, phosphates, and so on) in tap water, giving you pure, healthy water for your aquarium. If your RO product water is pure, your aquarium should have minimal algae growth, a steady pH level, and low phosphate and nitrate levels. If these conditions change, check your RO product water purity using one of the following methods:

• Use a conductivity meter (TDS meter), which will accurately measure the amount of impurities in the RO product water. Whereas regular tap water will have a reading in the range of 300-500, purified water should be in the range of 5-25.

• Measure the general hardness, alkalinity, and pH of the water with a test kit. Purified water will have a general hardness of 0 GH, alkalinity of 0 dKH, and a pH of 7.0. If your test values vary from those described above, you may need to replace the membrane.

The lifespan of the RO membrane depends upon the quality of your source water. Under most conditions, an RO membrane will produce about 25,000 gallons of purified water and last 2-3 years. However, high concentrations of certain minerals such as calcium, iron, and magnesium will shorten the lifespan of the membrane.

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