Ultra-low water loss and remarkable energy saving: At an economic flow rate (2 m/s), the head loss is less than 4 mH O.Air 2 gap isolation and automatic drainage: When the main valve is closed, the drainer automatically opens to drain the intermediate chamber, achieving air gap or zero-pressure isolation between the upstream and downstream of the main valve, ensuring safe and reliable isolation performance. Material-saving and flexible installation: Compact in size and light in weight, with a st