It is estimated that VOCs are present in one-fifth of the nation's water supplies. These impurities can have significant health and environmental effects, entering ground water from a variety of sources, including gasoline or oil spills, leaking underground fuel tanks, septic system cleaners, and chemicals used in the dry-cleaning industry. While designed for your WP-4V or WP4V-50, the Watts Premier RO Pure Plus VOC Carbon Block Water Post-Filter fits all standard 10-inch housings for under sink home water filtration. It is specifically formulated for the reduction of VOCs, filtering particles as small as 1-micron. This package includes one 1-Micron VOC Carbon Block Post-Filter (WP101013) with a flow rate of 0.5 GPM (1.89 lpm). Made with high quality, NSF-certified coconut shell activated carbon, this filter reduces a wide range of impurities. In addition to removing VOCs, this filter improves the taste of water and removes unwanted odors. Drinking water enters this filter after the water storage tank and acts as a final polishing filter to crispen up the flavor and enhance the taste of your water. This durable filter is crafted from high-quality materials for maximum filtration. Filter life may vary based upon local water conditions or use patterns, but we recommend replacing the VOC Carbon Post-Filter once a year.