Drips/trickles are generally single outlet devices positioned at the tree or plant root zone along a polyethylene (PE) lateral line.

The water in the drip/trickle follows a fine labyrinth with a zigzag path, which creates a pressure loss (see pictures). The cross sectional area in which the water flows is thereby larger and these emitters are less vulnerable to clogging. The usual flow rates are 1-2-4-6-8-12-16 L/hr at a pressure range between 0.5 - 4.0 bar. The tube diameter can be 12-16-20-22 mm and the emitter spacing 0.3-0.4-0.5-0.6-0.75-1.0-1.25-1.5 m.

The manufacturers' catalogue usually shows the size of the tube, the possible spacings of the emitters, the flow rate of the dripper, the operational pressure and the maximum length of the lateral.

Depending on how the emitters are placed in the plastic PE distribution line, the drip can be as a line source - in line or a point source -  on line.

The line source/in line type emitters are placed internally in equally spaced holes or slits made along the line (see pictures). Water applied from the close and equally spaced holes usually runs along the line and forms a continuous wetting pattern. This wetting pattern is suited for any row crops (see pictures).

The point source/on line type emitters are attached external to the lateral pipe.  Water applied from the point source emitters dissipate water pressure through a long, narrow path and a vortex chamber or a small orifice before discharging into the air. Usually forms a round deep wetting spot (see picture). The point source wetting pattern is suited for widely spaced plants in orchards, vineyards and for landscape trees or shrubs (see pictures).

Non pressure compensating dripper's flow rate varies directly with the pressure. Output from drippers is generally controlled by the size of the outlet and the length. Manufacturers generally give the variation in discharge rate from the dripper with changes in pressure in the lateral.

Pressure compensating drippers (PC) generally contain a flexible sleeve or diaphragm within the dripper. As pressure rises the sleeve is forced into the moulded thread of the dripper flow pathway, increasing the friction loss and compensating for higher pressure. Compensating drippers do not compensate for low pressure and where is used on flat land.

Pressure compensating non-drain (PCND) is similar to PC but has built in a non-drain device which eliminates water draining from the drip line when irrigation is stopped.

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