REVERSE OSMOSIS

Reverse osmosis (RO) systems force water, under pressure, into a module that contains a semipermeable membrane and a number of other filtration steps. A typical RO system has a prefilter designed to capture larger particles, chlorine, and other substances; a semipermeable membrane that captures more contaminants; an activated carbon filter that removes residual taste, odor, and some organic contaminants; and a storage tank to hold the treated water for use.

RO systems are commonly installed near the point-of-use, such as on a counter top or under a sink. They’re great for treating water for cooking and drinking, but they don’t usually produce large amounts of treated water — more like 3 to 10 gallons a day. For that reason, typically people choose to install RO-treated faucets in the most popular areas of the home such as kitchens and bathrooms, as opposed to installing it for every drinking tap. Just like any other kind of filter technology, RO systems require regular maintenance. That includes periodically replacing the unit’s prefilters, postfilters, and membrane modules.

WATER SOFTENERS

Ion exchange water softeners are among the most common ways of softening water. The typical ion exchange system consists of a pressure tank filled with sulfonated, polystyrene beads that are capable of removing hardness ions from water and replacing them with softer ions, such as sodium. These units are connected to a brine tank that’s filled with salt, which periodically regenerates the resin beads. The unit’s tiny beads attract and hold onto calcium and magnesium ions as water passes through them. When the beads become so saturated they can’t hold any more, the unit rinses them with salt, which scrubs off the mineral deposits and gets them ready to absorb hardness ions again. If you own this type of water softener, you can set it to regenerate at preset times. More sophisticated units can base their regeneration on your actual water use.