Filter screens work by blocking particles that are larger than the openings in the screen. The mesh number tells you how many openings there are per inch, so a higher mesh means smaller openings and finer filtration. In irrigation, you want enough filtration to protect emitters from sand and sediment, but not so fine that every drop in pressure and every cleaning becomes a problem. A mesh range of 120 to 200 is a common middle ground. It provides openings small enough to catch most sand and silt that can cause emitter clogging, while still allowing a reasonable flow rate through the system. If you use a coarser screen, larger particles can pass through and risk clogging later. If you use a much finer screen, the flow is more restricted and maintenance increases because debris builds up faster and pressure losses rise. So 120–200 mesh is widely used because it balances protection with practical flow and cleaning needs.

Friction loss in a fixed pipe rises as you push more water through it. As flow increases, the water speed (velocity) through the pipe goes up, and the energy dissipated by friction grows roughly with the square of that velocity. In standard pipe flow equations, friction loss per length is proportional to v^2, so doubling the flow roughly quadruples the friction loss. Because the diameter is held constant in this scenario, changing the flow changes velocity and therefore changes friction loss. The idea that friction loss only changes when diameter changes isn’t accurate for a fixed pipe, since increasing flow alone already modifies the losses.

Back pressure comes from extra push on the line caused by higher pressure on the discharge side. When a reservoir overflows, the water surface is higher and adds hydrostatic head to the piping. That extra head raises the pressure in the line, which can push back toward the source and create back pressure. The other options describe transient or different pressure effects: water hammer is a sudden, temporary surge from rapid valve changes; air in the pipes can cause flow issues but not sustained back pressure; leaks typically reduce pressure rather than create it. So the overflow of the reservoir is the situation that increases the line pressure enough to produce back pressure.

Protecting irrigation wiring from damage and moisture is the main idea. Burying low-voltage conductors about six inches below grade provides a practical balance: it shields the wires from mowing, digging, and other landscaping activities while keeping them accessible for maintenance. Shallow burial like two or four inches leaves wires prone to being nicked or cut, increasing the risk of shorts or a failed circuit. Deeper burial, such as twelve inches, adds more protection but isn’t usually required for standard residential systems and adds extra labor unless local codes or frost considerations require it. Therefore, six inches is the standard depth recommended.