Pressure reduction overflow valve and waterway system

The utility model relates to the field of valve body structures, and provides a pressure-reducing overflow valve and a waterway system.The pressure-reducing overflow valve is characterized in that a liquid inlet, a pressure-reducing opening and an overflow opening are formed in a valve body; the pressure reducing assembly is arranged in the valve body, and in the pressure reducing state, the pressure reducing assembly communicates with the liquid inlet and the pressure reducing opening; the overflow assembly is arranged in the valve body, in the pressure reduction state, the overflow assembly makes contact with the pressure reduction assembly, and the overflow assembly blocks the overflow opening; and in an overflow state, the pressure reducing port is communicated with the overflow port. In order to overcome the defect that in the prior art, an existing water-based pressure reducing valve does not have a high-pressure overflow protection function, according to the pressure reducing overflow valve, a pressure