国产熟妇AAA成人精品,囯产精品久久久久久久,91精品人妻人人爽,国产做a爰片毛片A片美国

Overview:The built-in anti backflow device in the pipe is composed of a stainless steel shell, synthetic rubber membrane flap, fasteners, etc. The synthetic rubber membrane flap tightly adheres to the inner wa

Overview:The built-in anti backflow device in the pipe is composed of a stainless steel shell, synthetic rubber membrane flap, fasteners, etc. The synthetic rubber membrane flap tightly adheres to the inner wall of the pipeline in the absence of water flow, preventing any fluid from flowing from downstream to upstream. When the pressure inside the pipeline reaches a certain level, the membrane flap will open under the action of pressure, causing it to open and allow the fluid to flow.