PURPOSE:To eliminate the need of priming water and enable the start of a while pool by connecting the lower portion of water in a bath to the air phase part of the upper part of a feed water tank via a lifting pipe, connecting the delivery outlet of a pump to the lower portion of water in the bath via a delivery pipe, and providing the air outlet of an air discharge pipe on a feed water pipe. CONSTITUTION:A feed water tank 2 is supplied with water up to a water level A and a bath 4 contains the required amount of water. When a pump 3 is operated in the aforesaid state, water in the feed water tank 2 gushes onto water in the bath 4 by the predetermined amount due to the operation of the pump 3, via the route of a suction pipe 7, the pump 3, a delivery pipe 6 and the jet nozzle bath 4. Air stagnat ing in a lift pipe 5 enters the feed water tank 2 and air pressure at the air phase part G of the tank 2 drops. Consequently, the water level A temporarily drops to a level A1, and water flows from the lift pipe 5 to the tank 2. When the pump 5 is stopped, the water level returns to A due to an inflow from the lift pipe 5, because the air phase part G of the feed water tank 2 is in a negative pressure condition. As a result, the air pressure of the said part G returns to an original state. Also, water retained in the pump 3 can be properly maintained by locating the pump 3 below the water level A, and the smooth start of a while pool is guaranteed.
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