A sprinkling or irrigation system includes a sprinkler controller that is capable of detecting a leak in one or more zones of the system. The system include a main valve and an adjustable valve in a bypass line around the main valve. The adjustable valve is set to a partially closed state such that a selected on of the zones produces a pressure at a selected proportion of the static pressure provided by the water source such as half the static pressure. A leak is detected when a zone, with the main valve closed and the adjustable valve in the partially closed state, produced a test pressure that is substantially lower than the selected proportion of the static pressure, as modified by a test factor.