Before you start digging a trench for the polypipe for the pop-up sprinklers, check with the authorities that there aren't any water, gas or electrical pipes or cables where you plan to dig. If needed, contact the relevant external body to find out if it's safe to dig in the area you want to.
The easiest way to roll out the poly pipe is to lay it at the edge of the garden where the irrigation is being installed. Use an irrigation pin to stick one end of the poly pipe firmly into the ground, then unroll the pipe until you reach the corner. Cut the poly pipe to length and pin it into the ground. Repeat this process until you have laid out and cut all of the poly pipe you need.
To make sure the poly pipe is cut to the right length, lay one pipe over the other and cut them with pipe cutters where they meet. Slide a locking clamp over the end of each piece of poly pipe. To make fitting the elbow into the poly pipe easier, dip the pipe end in hot water to soften it. Once soft enough insert the elbow into both ends of the poly pipe to join them together. Slide the locking clamps into place and tighten them with the pliers. Repeat this process until all of the pipe is connected.
Wrap Teflon tape around the elbow where the pop-up sprinkler will be attached. This will make sure the seal between the two is tight. Screw the pop-up sprinkler into place, making sure it is as far down on the elbow as possible. Repeat this step for all of the pop-up sprinklers.
To seal the poly pipe at the end of the sprinkler, cut a short piece of polypipe and attach it to the elbow and hold it in place with a locking clamp. Attach an end piece to the end of this piece of pipe. This will give you the flexibility to add-on more poly pipe and pop-up sprinklers to your garden in the future.
Before you cover the pipes with soil, check that there are irrigation pins at regular intervals, about every metre, to hold it securely in place. Use your spade to cover the polypipe with soil and cover the sprinklers so that the top of them is at soil level.