Was not sure if this is the correct forum but here goes. I have a well, approx 45ft deep, at the bottom of which is a submersible pump. Was originally installed to run a sprinkler system for which it was fine. Now my wife wants to use the water for general garden spraying using a hand held spray. The problem is she switches the pump on then walks to the spray before using it. In the meantime whilst she is walking to the spray the pump is banging away against a dead head, as it will every time she releases the trigger on the spray gun. I have fuffed about with a flow switch on the pipe outlet to fire up the pump only when there is a demand but it is a chicken and egg scenario. No flow = no signal from flow switch= pump does not switch on. What I need is a pump like I have on the central heating , Grundfos, where if there is no flow ie trvs shut the pump just runs ever so slowly until a trv opens then it speeds up. Any idea?