How Does The North Star Reverse Osmosis System Work?
Reverse Osmosis is an excellent method of producing fresh, high quality drinking water.

These systems actually filter water then force it through a thin film, semi-permeable plastic membrane. Pressure from the home's water system provides the pressure needed to push the water through the membrane. A small stream of water is used to flush the rejected impurities from the membrane surface and down the drain. Up to 99% of all dissolved solids are removed.

Reverse Osmosis (RO) was first introduced to purify seawater to make it potable. It can remove virtually 90-99% of particles and ions. In general, reverse osmosis filtration restricts the flow of everything except water through a special type of membrane and allows oxygen to pass so product water doesn't taste flat like boiled or distilled water.

The RO filter is called a membrane filter because it works just like a natural membrane that surrounds a living cell. It is semi-permeable, allowing some molecules to go through the filter.

1. Prefilter removes sediment and particulate matter from your tap water.
2. Water is forced through reverse osmosis membrane reducing most dissolved solids.
3. Water is stored in the expandable storage chamber awaiting your needs.
4. When water is drawn from the storage chamber it goes through a final polishing filter to reduce taste and odors before flowing through your faucet.

How The RO Membrane Works

The semi-permeable membrane is wrapped around a hollow cylindrical core. Feed water flows along the surface of the membrane. A flow restrictor limits the feed water flow rate creating back pressure that forces some of the water through the semi-permeable membrane.

Once inside the membrane, the filtered product water follows the inside of the envelope to the core. The water that doesn't pass through sweeps the filtered dirt, particles and debris from the membrane surface and carries the residue down the drain.

Feed Water

Feed water is the key to the quality and production of the reverse osmosis filtration system. The following specifications should always be met:

• Feed water: PSI 40 - 125 PSI
• Feed water Temperature: 40 - 100 (F)
• Max. Total Dissolved Solids (TDS): 2000 ppm
• Max. Hardness: 10 gpg
• Max. Iron, Hydrogen Sulfide, Manganese: 0 ppm
• pH limits: 4 - 10
• Chlorine allowable:2 ppm

The Prefilter

The prefilter is a replaceable activated carbon sediment filter. The filter is necessary to remove sediment that would otherwise clog the RO membrane and chlorine that would destroy the membrane. After a time, the prefilter begins to plug and water cannot get through it as fast which eventually slows water production. The prefilter will remove:

• Up to 5 microns of sediment (dirt, sand, silt, etc.)
• 2 ppm chlorine taste and odor

Prefilters should generally be changed every 6 months depending on water usage and the chlorine levels in the water.

The Postfilter

The activated carbon postfilter polishes of the product water. It will remove most unpleasant tastes and odors and sediment. The water passes through this final filtering process immediately before going to the faucet.

Postfilters should generally be changed every 6 months depending on water usage and the chlorine levels in the water.

Automatic Shutoff

To conserve water, the drinking system has an automatic shutoff that functions by pressure. The automatic shutoff consists of 2 diaphragms and a plunger. The plunger moves up or down in the housing based upon diaphragm pressures.

The lower diaphragm pushes the plunger up allowing feed water to flow through the inlet/outlet port until the storage area pressure exceeds one half the inlet pressure. At this point, the storage area pressure on the upper diaphragm is great enough to push the plunger down stopping the flow of feed water. Flow will not start again until the storage area pressure drops because of water withdrawal at the faucet.

The RO Membrane Cartridge

The RO cartridge is a tightly wound semi-permeable membrane. When water is forced through the membrane, it flows only one way down into the cartridge. This high quality product water is directed into the storage area or out to the faucet. The membrane has 2 O-rings on one end that fits into the check valve. Rejected water flushes the membrane surface and carries the dissolved solids to the drain.