Make sure the discharge of this valve is directed to an open drain and protected from freezing.
要确保阀门排泄的水直接排放到一个畅通的排水口，并保证不会冻结。
A land drain is usually a pipe buried in farm land but it may also be an open channel.
农田的排水系统通常是埋在农田中的管子，但也可以是明渠。
A land drain is usually a pipe buried in farm land but it may also be an open channel.
农田的排水系统通常是埋在农田中的管子，但也可以是明渠。
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