MIR02 – 22ft Overhead Twin Line Irrigation

Overhead Irrigation

This system involves the water supply entering at one side of the polytunnel on an intermediate hoop (preferably the centre hoop but can be any intermediate hoop). The supply is then distributed down 4 lines each independently controlled through a manual ball valve. If the water supply cannot accommodate all 4 lines at once, then up to 3 lines can be isolated to increase supply to the other one. This has the added advantage of only watering areas of the polytunnel in use (fig 27a)

Overhead Spray Line

To support the system, two straining wires are run down the length of the polytunnel, these should be placed to divide the polytunnel equally into three. The end of each wire should be taken around the metal door rail (fig 26b).

At the other end of the polytunnel a short piece of wire (approximately 30-45cm) should be positioned similarly, with a wire tensioner on the free end. Feed the first straining wire through the tensioner and tension until the wire is straight (fig 25c). To support the wire at the point where it passes below an intermediate hoop, cut a length of wire 30cm longer than the gap between the underside of the hoop and the straining wire (fig 25d). Bend this wire at one end into a small loop and, using a cable tie through the loop, fix this wire to the hoop, bend the other end around the full-length straining wire ensuring that the wire is at a level position (fig 25e).

Overhead Pipework

Cut two lengths of 25mm pipe the length of you polytunnel and place a male plug in each end. To fit the male plug, slide the coupling nut onto the pipe (tapered end first) push the grip ring (red) into the end of the pipe, these barbed fittings are a tight fit and may require some force to fully press home.

Push the male plug onto the grip ring/pipe and screw on the coupling nut and hand tighten (fig 27g). Suspend these two pipes from the straining wire using the plastic support hooks placed every 60cm (fig 27h). Choose the intermediate hoop where your water supply will enter (fig 27i). At the point directly under the hoop remove 30cm piece (15cm either side of the hoop centre) of the 25mm pipe (in effect you should split the two lengths of pipe into four). Assemble the two distribution tees and ball valves, using the PTFE tape on the joints between the two (fig 27j). Now use this assembly to join the pipes back together using the grip rings (red) and coupling nuts as described above.

Water inlet System

Assemble the inlet system, making sure the water flow follows the direction arrows stamped on the filter. PTFE tape should be placed around the thread end of the filter (fig 27k/l).  Fix an elbow to the end of the remaining 25mm pipe using the grip rings (red) and coupling nuts. Using the cable ties supplied strap this pipe to the underside of the intermediate hoop, approx. every 50cm with the elbow directly over the spray line furthest away from the water inlet (fig 27m).

Cut the pipe where it goes over the next spray line (nearest the water inlet) and fit a tee (fig 26n). The pipework should then run along the underside of the hoop to the side where it should be fix to the filter and Ball Valve using an insert and coupling nut.

Water Connecting Pipes

Cut two pieces of the remaining pipe and join each of the spray lines to the header pipe to complete the system.

Spray Nozzles

Punch a hole in the underside of the spray line centrally between each hoop (fig 27o). Insert a down tube adaptor in each hole using the punch for assistance. Assemble the down tube and spray nozzle (fig 27p) and insert into each of the adaptors. Note the direction of flow on the Anti drip valve.

Prestige Overhead Irrigation 

If you ordered a Prestige Irrigation System, then you will need to fit the Water Controller onto the tap of your water source. The water controller is supplied with fittings for either a 3/4in or 1in male threaded tap. Use the two ‘Hose to Female Click’ fittings to run a hose between the ‘Male Click’ fittings on the Water Controller and the Polytunnel. You will require a hose pipe and may require extra ‘Click’ fittings depending on the type of tap being used.