Model994 BLT Portable Hydrant Backflow Preventer meets the design requirements of most national standards. Due to the portability of the unit, there are no national approvals available.是什么意思_Model994 BLT Portable Hydrant Backflow Preventer meets the design requirements of most national standards. Due to the portability of the unit, there are no national approvals available.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句