This is an important topic, Lewis, and one worth bringing up. The concept behind ancient plumbing can help us locate the Holy Temple's original location. The water entered at Wilson's arch and travelled via aqueducts to various points on the temple compound. By definition, an aqueduct is a channel that brings water to a location, usually open. This is important because so many people today think the Dome of the Rock is where the temple was located, but if so, then the open water would have to run uphill 20 meters. The only way this is possible was if some of the aqueducts were sealed and maybe ran through an inverted syphon. As long as the water supply (a distant lake) is higher than the end point this would work. An inverted syphon, much like your trap in a sink drain, was prone to get clogged, however.
Important equations plumbers use to calculate water flow and pressure is the source's "head". In physics, potential energy E=mgh where m is mass, g gravitational acceleration, and h is the height. A similar formula for the pressure (head) is P=ρgh where ρ (rho) is the density of the fluid, and g and h are the same. Thus, you can calculate water pressure of a water tower, say, 50 feet off the ground. Modern electrical pumps give "head" mechanically. This is static pressure and pressure is the measure of force per unit area, which is the same as energy contained in a given volume of fluid.
As for flow, I won't get into the details of the math as it's a bit more complex, but there's something called Bernoulli's equations that states the static and dynamic (moving water) pressures are a constant. There's also a useful formula plumbers use to calculate the pressure drop from friction in a pipe given a certain water flow rate. This is the Darcy- Weisbach equation and is analogues to electronics where voltage (pressure) = current(flow) X resistance.
