This paper investigates the pressure response of fluid in small-bore piping under seismic conditions. We conducted experiments to determine the influence of flexible piping on the pressure response. Our test models consisted of a single pipe and a tank, both containing fluid (water). One model had a pipe that was entirely rigid, while the other model had a pipe with one flexible section. The natural frequency of the partially flexible pipe, when empty, was close to that of the fluid contained in the entirely rigid pipe. The pressure was raised using either a shaking table or a pulsation generator, and either artificial earthquakes or sinusoidal waves as input. The results showed that in some cases the pressure responses of the flexible-piping model were larger than those of the all-rigid piping model. Numerical analysis using the finite element method agreed well with the experimental results.