30.10.14: I have been constructing a vertical farm on my garage wall, facing south. As the wall is under the shelter of the eaves, it is necessary to fit a watering system, to trickle rainwater through the farm. In the summer this is a specially necessary, but in the winter it is necessary to close the valve when weather is too rainy, to avoid over watering.
It is too high to reach to water the upper bottles with a watering can. The hoods above the bottles are designed to reduce the amount of watering can water going on the wall instead of into the bottles.
I am recycling 4 pint milk bottles (2.227 litres), which seem to offer an idea height to width ratio for water and nutrient retention. After a while, I will have to water them with liquid plant feed, perhaps.
Here is the start of laying in 22mm copper pipes for the watering system, using the garage gutter as a storage vessel.