A check valve (3) can prevent the natural chemical absorption water head of the water head when the manual pump or the mechanical pump stops to work.

止回阀(3)起当手压或机械泵停止工作时能阻止水位差的自然吸药。

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My recommendations would be Christiania, the swimming area at Islands Brygge (where you can take a dip in the cool, clean salt-water of the Copenhagen channel), or rent a bike and head north along the coast towards the beaches in Klampenborg and beyond, while looking at the magnificent houses along the way.

CNN: Copenhagen: A local's view

He was able to pull Krymzen up onto the ice, but the current was carrying Samara downstream, about 4 or 5 feet from the edge of the ice, her head going in and out of the water, Shaw told a press conference Monday.

CNN: Hero dog helps pull girl from icy river