Most reverse osmosis units are equipped with pre filters that retain particles such as chlorine that could damage the membrane. The membrane is the heart of the system and must be closely monitored to ensure its efficiency and prolong its life. It is made of polymers and its pores measure around ten thousandths of a micron, allowing it to retain 99% of bacteria and between 85 to 99% of the minerals present in water.
The efficiency of a reverse osmosis unit is determined by the regular cleaning of the membrane to prevent it from clogging. Calcium carbonate of limestone is the most common clogging element. Normally a m embrane can filter about 25,000 gallons of water: or about 3-5 years of service before it needs replacing.