Since the hydrostatic pressure p in open vessels remains constant, the influence of the temperature has a negative effect on the measurement result. Therefore, the measured hydrostatic pressure of a liquid should always be correlated to the medium temperature.

How does temperature affect pressure in a hydrostatic test?

A rise in temperature of the pipe wall and test liquid causes circumferential expansion of the pipe wall and also an increase in volume of the test liquid. The combined effect of these expansions has the same effect as pumping additional water into the test section and will cause an increase in pressure.

Does fluid pressure increase with temperature?

As the temperature of a liquid increases, the kinetic energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, thereby increasing the vapor pressure.