After shutoff valves are closed, open test cock #2, #3 and #4 to relieve pressure within the backflow assembly.
After shutoff valves are closed, open test cock #2, #3 and #4 to relieve pressure within the backflow assembly.
在关闭了关闭阀后，开启测试旋塞2号，3号和4号，释放回流阀总成的压力。