After the supply lines are installed, drip irrigation installation is the same whether you use surface or subsurface supply lines. Start off by staking out the positions of the header lines, drain lines, and lateral lines. Next, cut 1/2-inch poly pipe to the proper length and place it along the strings indicating its position.
Installing Parallel Lines
Header lines and drain lines require solid (unpierced) poly pipe. Some people prefer to use PVC pipe for both. Lateral lines, however, can be made of emitter line, porous pipe, or solid poly pipe to which you can then add emitters.
Cut the header line as needed and insert tees or elbows where the laterals join it. If you’ve used compression fittings most commonly supplied with drip irrigation kits, assemble by simultaneously pushing and twisting the pipe into the fitting. For instructions on installing other kinds of connectors, see Working with Vinyl Tubing. Now connect the lateral lines to the header line and flush until the water runs clear.
Next, assemble the drain line at the opposite end of the laterals, in the same way as the header. Extend one line about 12 inches beyond the rectangle formed by the header and drainage lines for use as an end-closure extension. If you choose not to use a drain line, leave 12 inches of spare poly pipe at the end of each lateral line for end closure. Flush again.
Install an end closure at each unattached lateral line. Figure-8 end closures are popular. To install, insert the end closure over the pipe, then bend back the end of the pipe and insert it in the other opening of the figure 8, pinching off water circulation. A drawback of the figure 8 is that the bent section of the pipe may eventually crack. A hose end plug costs more, but is longer lasting. Insert the end of the lateral line into the compression fitting of the end plug. The cap can then be screwed on or off as needed. Always place end closures at the lowest part in the system.
Installing Lines for Isolated Plantings
Lay out the 1/2-inch poly pipe as determined in your plan (see Planning Drip Systems), starting with the supply line, then the laterals, and finally any feeder lines, using tees and elbows as needed to connect the lines. Pin them down with metal or wooden stakes, if necessary. Insert drip emitters within the lines as needed. Any sections that have no emitters can be buried 6 inches deep or more. Flush well.
Terminate each unconnected line with an end closure.
At this point, drip emitters can be inserted into the lateral lines using a special hole punch. Formerly one emitter was placed at the base of each plant, but years of experience have shown that plants grow better when the entire root zone is kept evenly moist. to achieve this, space emitters regularly along the entire length of the lateral line rather than applying water to individual plants.
Only where plants are spaced well apart should emitters be used at the rate of one per plant. The chart below gives suggestions for placement.
Drip Emitter Placement
|Soil Type||Emitter Flow||Plant Spacing||Emitter Placement|
|Clay||1/2 gph||Up to 24″||Every 24″|
|25″ or more||1 per plant*|
|Loam||1 gph||Up to 18″||Every 18″|
|19″ or more||1 per plant*|
|Sand||2 gph||Up to 12″||Every 12″|
|13″ or more||1 per plant*|
*For small- and medium-sized plants. For shrubs, trees, and other large plants, see Number of Emitters per Plant Based on Canopy Diameter in Planning Drip Systems.