In the discussion on piezometers with ideal fluids, it is established that an inviscid fluid flowing in a horizontal pipe does not cause fluid to rise in piezometers, as the pressure remains equal to atmospheric pressure throughout. In contrast, a viscous fluid experiences a pressure drop along the pipe, allowing fluid to rise in piezometers due to the pressure gradient created by viscous drag. The pressure at points within the pipe varies, with higher pressures upstream compared to downstream, particularly in constricted sections. The conversation also clarifies that the gauge pressure in piezometers is influenced by the flow conditions and the fluid's viscosity. Overall, the application of Bernoulli's equation and the understanding of pressure dynamics in fluid flow are central to the discussion.