Two basic types of filters are graduated sand filters and screen filters. At least one stage of filtration is needed for microirrigation systems. Drip irrigation systems usually require more filtration than microsprinklers. The required screen size or sand filter size is determined by the type, size, and concentration of contaminants in the water source, required quality of filtered water, flow rate, and cost analysis. The type of drippers or emitters also affects the level of required filtration.
Filters require periodic backflushing depending on the amount of contamination in the water.
Backflushing can be done manually or automatically. Any water-soluble fertilizer may be injected through a microirrigation system. A pressure differential can be used to cause flow through a tank as shown in Figure 2, or a nutrient metering pump can be used to carefully control fertilizer application. In either case, inject fertilizer in advance of the filter to remove undissolved chemicals. Microirrigation systems operate at relatively low pressure compared to sprinkler irrigation.