APEC, Advanced Purification Engineering Corp. APEC is the leading manufacturer of residential reverse osmosis drinking water filtration systems in the United States. We are based out of the City of Industry, California where we design and assemble our famous Reverse Osmosis Systems With more than 20 years of industry experience and a loyal customer base that spans the globe, we are proud of our unbeatable reputation in delivering the highest quality water filtration systems. Our products are shipped worldwide to treat all types of water problems and have been employed successfully for a variety of residential, commercial and industrial applications.