Most are manually operated valves (by hand) or mechanically controlled (pressure/vacuum or float level).
Most are manually operated valves (by hand) or mechanically controlled (pressure/vacuum or float level).
大部分为手动阀门或机械控制阀（压力/真空或浮子度）。
Most are manually operated valves (by hand) or mechanically controlled (pressure/vacuum or float level).
大部分为手动阀门或机械控制阀（压力/真空或浮子度）。