Many thanks for your recent enquiry concerning a suitable irrigation system for your polytunnel and beds. You seem to have worked out the answer for yourself and I’d certainly agree that the soaker hose takes some beating for efficient water distribution from a low pressure source.
Just to confirm, water will spread around 50cm either side from the soaker hose in cultivated soil so when calculating the length of hose you will require, allow 1m between loops. It’s this spacing that makes the hose economically attractive as well as efficient and as the soaker hose is the same diameter as a standard garden hose (½”) extra lengths can easily be added if required as all off the shelf hose fixings are compatible; that’s connectors, joints, the lot!
So the soaker hose is certainly my recommendation – the drip feed, small diameter piping which forms the Raised Bed Irrigation Kit and other similar products really comes into its own in tight small spaces – and I’d certainly try the minimum spacing to begin with.
I trust this information is of help but if there’s anything else you’d like to know them please don’t hesitate to ask; many thanks once again for your enquiry and the best of luck with your growing - and irrigating - activities this year.