The Resistance to Liquid Pressure Test Stand (RLPTS) is designed to evaluate the performance of radial flow nuclear-grade HEPA filters with liquid pressures up to 225 inches water column. In particular, the RLPTS utilizes a viscous liquid to challenge filter to elevated differential pressures. The RLPTS consists of four main test sections, including two separate flow paths for air and liquid, a storage tank that holds the viscous liquid, and the filter housing that holds the test filter. The airflow path operates in an open circuit arrangement, with an induced draft fan at the exhaust end to draw air through the system. The liquid flow path uses a closed circuit arrangement, where the viscous liquid flows in a loop and is continuously reused. The filter housing employs flanged pipe connections for both the air and the viscous liquid flow paths that allow for changing from air to liquid testing, or back again from liquid to air.