It was in fact, the end of Mine and Louise's greenhouse cycle as we'd got the allotment late and had nothing left to grow, however in the last two weeks we've started planting out cauliflower, red onions and parsnips in the spare bedroom so will shortly need to use the system again.
So I called back the technical support of Alastair, and alas during testing (We're well disciplined technicians) the closing of the tap by the servo was failing. It appeared that the servo was struggling on its return either because the tap was stiff or there wasn't enough power.
Alastair - being the Einstein he is - suggested we tested the force the servo would need in order to turn the tap. So our first test was to thread string around the handle roughly 1cm from the pivot point. We then hung a plastic cup from this and slowly added water.
|Test 1: Cup on a string and add water|
|Knots are tricky|
So we decided to just up the ante and use a more powerful servo. Which we had planned to do when we first saw it wasn't working.