Serious backyard flooding. 6 Valve system, 4 in backyard and system keeps coming on for long duration (typically at night) and flooding occurs. I replaced the timer, had a rewire of the valves in back..(sheath exposed, copper wires touching). Service company unscrewed each of the four valves and tested for leakage - none detected (nothing more than pushing down on the water inside the valve and seeing if it "overflowed"). All 4 systems come on with good pressure. Totally frustrated on what to do next. The timer system is definately in the off position. Any help much appreciated.