Sloppin' Bob

We have a polytunnel. At 17m x 9m its footprint is quite a bit bigger than the 2-floor area of our house. At one time we had a straggly grapevine trained up a trellis inside the tunnel. A friend, who knows a thing or two about wine came to view the tunnel when it was new and the plastic was clear and clean. I asked him: if were were to propagate our vine and have a 17m run of plants suitably pruned and fed and cared for, how much wine might we get in a good year? Oh, he replied, a bottle a day with a following wind. We contrived to kill our little vine shortly thereafter. But for nearly 20 years, we've had on-again off-again success with green beans and tomatoes and courgettes. And a mighty triffid of a rosemary bush.We do have a garden-tap in one corner which ultimately comes from our domestic 30m deep borehole but I'd rather use rainwater which falls on the plastic and gets guttered into various receptacles. Years ago, I bought 50m of perforated pipe with the intention of…