The system of water reticulation illustrated here shows how to overcome the problem of a water supply, such as a spring or rainwater tank, that would be pumped dry if there were not some method to control the draw-off rate until the supply had been replenished naturally.
The overflow return system allows the use of 15mm low density (or garden hose) return lines and does away with the need to either stop the windmill or fit a costly, and potentially troublesome, relief valve and ballcock system for when the reservoir is full.