5. Does a reverse osmosis system remove biological contaminants?

RO systems are capable of removing certain biological contaminants such as Cryptosporidium and Giardia. The pore size of the RO membrane along with the amount of pressure applied to the water will generally determine the rate of reduction of such contaminants. The Water Quality Association (WQA) cautions, however, that while RO membranes are reliable for treatment of a range of health contaminants, design considerations such as tiny seal leaks or manufacturing imperfections may prevent a unit from offering foolproof protection against biological contaminants for consumer drinking water systems. Therefore, WQA suggests that absolute disinfectant (a reduction of contaminants greater than 99.9 percent) be ensured with cyst-rated and certified products and post-disinfection systems such as ultraviolet light. NOTE: In California, State law requires that any reverse osmosis manufacturer or installer making specific health claims for a drinking water product must have that product tested and certified by a State approved lab.