Disclosed herein are methods for reducing fouling caused by process water present within a water recycling loop of a pyrolysis plant. The process water includes water, a pygas, and in some cases pygas byproducts. Fouling is caused by phase separation and accumulation of materials from the process water on equipment surfaces. The method includes applying a total of about 5 ppm to 500 ppm of one or more antifouling polymers to the process water to form a treated process water. The one or more antifouling polymers are selected from the group consisting of copolymers of unsaturated fatty acids, primary diamines, and acrylic acid; copolymers of methacrylamidopropyl trimethylammonium chloride with acrylic acid and/or acrylamide; copolymers of ethylene glycol and propylene glycol; and blends of two or more thereof.