WETS Irrigation Technician Practice Exam

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.