常见例句雙語例句The backflow preventer must be installed upstream of the regulator.防倒流裝置必須安裝在調節閥的上遊位置。The relief valve may be serviced while on or off the backflow preventer valve.可以在防廻流閥上維脩安全閥,或將其從防廻流閥拆卸下來維脩。 返回 backflow preventer