11/6/26 - Harvesting Water Off The Polytunnel
Good evening and thanks for dropping by. A bit of an usually timed post going by normal standards, but that's what happens when you have time off work and get chance to visit the plot to do some worthwhile work when in normal circumstances, you'd be confined to the desk during the week.
Ever since the main polytunnel went into place over the winter before last, I've been looking for a way to harvest rainwater off it. There is a very simple and well documented way to do this IF you have a timber rail running around your polytunnel, about 1.5 meters above the ground. To keep costs down at the point of purchase, I didn't choose that option as realistically, it would serve no purpose for growing. So there was a need to look for an alternative.
At home, we have many water butts attached to the house and sheds. Once of these water butts get little use because it's tucked out the way and it takes a bit of clambering to get to it. I decided to empty that water butt out and take it up to the plot to become the main receptacle to store the water.
Mindful that while there is no water in it, it is very likely that it can be blown over, I've used some metal stakes and some old abseil rope to hold it into place.
Looking over the internet, there are plenty of ideas and methods people have devised to collect water of polytunnels. Many of them assume that you have a wooden rail or some way of securing or supporting traditional length of guttering that you would normally have around a shed or house. While this would be an ideal and long lasting solution, it's also a bit expensive. But there are other ways that I come across, initially just by searching on Amazon's website. When I searched for small guttering, I came across flexible self-adhesive guttering, intended for use around motorhomes and caravans. It's made from flexible rubber come plastic material that would usually just stick to the side of the vehicle, and channel the water away from door frames and windows etc. Returning to more general searching online, I started to see videos of people using this type of guttering to stick to the side of their tunnel. After more searching, I also found a polytunnel store (Northern Polytunnels) who actually sold the same flexible guttering on their site, only it was marked up a fair bit compared to what was available elsewhere. But this did confirm that it was a good way to go solution wise.
I ordered initially what I thought was a 5 meter length, enough to run down one side of the tunnel. As it turns out, I actually ordered a 3 meter length, so left myself a little short. It doesn't really matter though. To make sure I had enough fall along the length of the guttering, I used a piece of string tied to each door frame ensuring the side where the water butt is positioned was significantly lower than the other end. Then I marked the points where the string touched the poles. The way the polythene stretches over the frame means that in between the poles, the plastic bows inwards a bit, so I also marked with a sharpie, points along the plastic where the string was furthest away from the plastic, so I had a clear guide of where the guttering needed to stick to.
Having measured and marked everything out, I peeled off the backing from the self-adhesive strip and started pushing the guttering onto the plastic of the polytunnel. In truth, I could have done with someone inside the polytunnel at this point to provide some equal pressure from the inside so I could make sure the guttering was stuck into place as best as possible. I still managed though. Once that was stuck into place, I still needed to secure it further. When I bought the mini polytunnel, I also bought a big role of polytunnel repair tape. This came in useful in this job too. I cut strips of repair tape, around 6 cm wide and half meter in length. Each strip I used to stick to the side of the polytunnel plastic, just above the guttering, and then overlap it into the profile of the guttering. As well as providing more adhesive security, it also provides a lip to channel water from the side of the tunnel down into the guttering.
The final piece of the puzzle was to attach some plastic pipe to the end of the guttering and push the pipe into the water butt to allow the water to flow in. A quick test with a sprinkling from a watering can showed the water being collected into the guttering, and then running down into the water butt. Happy days!
This solution obviously only collects water from less that half the surface area of the tunnel. I want to see how this goes. At the moment, I have only spent less than £15 for the project. If it works well though, I will probably get more guttering of a similar type, extend the current install so it runs the full length of the tunnel. Then, I will look at doing something similar over the other side of the tunnel. When it comes to doing that side though, I will also need to source another water butt. Time to keep an eye out for someone looking to get rid of one!