Nov 19, 2013 Snoop leak detection fluid viscosity test Snoop leak detection fluid viscosity test. Snoop leak detection fluid viscosity is similar to water. As soon as you apply, product runs off. Not with new Heavy-Duty Leak Detection Fluid. HD-LDF has much more viscosity and stays in place longer, even on vertical surfaces. Fresno Area Express Transit Authority, Fresno California uses Heavy-Duty Leak Detection Fluid. Their technicians noticed a reduction in product required to find leaks. LDF is viscous; it resists flow and stays in place. Other leak detection fluids run off, just like water. Save time, save money and get the job done right the first time with HD-LDF-C. "If you can't find a leak with this stuff, you don't have one."