If relief valve discharge due to a failure of the backflow preventer second check valve is a concern, a second Flood Protection - Shutdown Valve should be located immediately downstream of the backflow prevention assembly.

• 如果认为防回流阀的第二止回阀的故障导致安全阀排放现象应该得到处理，则应该在防回流阀总成下游立即安置第二堵漏-关闭阀。