| 摘要 |
PROBLEM TO BE SOLVED: To prevent freezing of a water conduit pipe for leading water from a water tank at a lower place to the water tank at a higher place at low cost. SOLUTION: Drain reserved at a lower sump 10 is pumped up by a submerged pump 12 and led to a precipitation water tank 16 provided at a higher place than the lower sump 10 through a drainpipe 14. When a water level of the lower sump 10 is raised and reaches the first level L1 or more during non- operation of the pump 12, the submerged pump 12 operates, and, when the water level is lowered and reaches the second level L2, the submerged pump 12 ceases to operate. The end part of the precipitation water tank 16 side of the drainpipe 14 is arranged so as to always locate at a lower position than the water level while the water level of the lower sump 10 is between the level L1 and L2.
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