WaterMate : Polytunnel pipework – Harvst

Every polytunnel is different, so you will need to adapt the guide for your own situation.

Most often, water is distributed around the perimeter of the polytunnel using a 13mm LDPE (semi rigid) pipe which is fixed to straining wires around 1m above the ground. Into this pipe, you can connect sprayers directly, or 4mm take-off hoses for drippers or other 4mm emitters.

Tools needed (not included)

Secateurs for cutting pipe
Pozidrive screwdriver and a selection of screws
Pliers to cut 2mm rubber coated straining wire
Small adjustable spanner
Kettle to warm water for softening pipe ends

WARNING The ends of the galvanised wire are sharp, and the wire will be under tension. Wear safety goggles and gloves, do not over tension the wire and take care not to pierce the plastic of your polytunnel.

Example : one perimeter pipe & one staging sprayer

Zone 1 as a perimeter pipe around the polytunnel with drippers or sprayers for a soaking of the larger plants, and zone 2 spraying or misting your seed trays and pots on the staging / shelves on a more regular basis, perhaps controlled by a wireless temperature/humidity sensor.

Installation process

Tip : To prevent the support wire causing heat damage where it comes into contact with your polytunnel skin, thread the wire through 4mm micro irrigation pipe first, or use a foam barrier between the wire and the polytunnel.

Using pliers or wire cutters, cut a short (30cm) section of wire and thread it through the small hole in the flat end of the wire tensioner. Using the wire, fix the tensioner to something strong at one end of the polytunnel, at least 1m above the ground.
Uncoil the wire, and secure one end at the same height at the other end of the polytunnel. A loop around a hoop with a good twist will do.
Straighten out the wire so that it reaches the tensioner, and cut it a little longer than needed. Don’t let the wire spring away and cut your polytunnel.
Thread the free end of the wire through the hole in the wire tensioner frame, and then through the hole in the tensioner barrel. See how the barrel spins just one way (against the ratchet mechanism), and feed the wire through appropriately.
Turn the tensioner barrel to tighten the wire. Not too tight.
Fix your LDPE perimeter pipe to the wire using cable ties every 30cm, making a full loop around the polytunnel.
Close the loop with a tee joint, and from the centre of the tee joint, take a length of flexible braided hose to one of the outlets on the water valves. The one with the yellow wire is zone 1, and the one with the black wire is zone 2. Secure it with a jubilee clip over the raised part of the barb.
Punch holes in the LDPE pipe and insert your emitters or take-off lines. We suggest about 50cm apart for sprayers.

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