CLOSING PLATE WITH BREATHING HOLE

PURPOSE:To enable water to be filled within a pipe and air to be discharged easily by providing an arc-shaped breathing groove on a single-side surface of a disc at a grip side and further by providing a breathing hole which connects the breathing groove and an outer-periphery part. CONSTITUTION:When filling water within a pipe 1, a water for test 7 flows into the pipe with a higher pressure than that at a lower part of the pipe 1 and a water level rises gradually to a higher position so that an air 8 within the pipe 1 does not form stagnation of air, reaches a terminal part of the pipe at a higher part, is discharged to an outside from a breathing hole 13 of a closing plate with breathing hole 10, and is substituted for the water for test 7. Therefore, at the start of water-filling, only air 8 is discharged from an air vent hose 22. However, after water 7 is filled into the pipe 1, the water 7 is overflown. This state can be visually inspected by making a hose 22 to be transparent and can be confirmed easily by delivery to a drain channel 23. After this, stopping valves of a water-filling pipe 18 and the hose 22, the hose 22 is removed from a screw 13a of the closing plate with breathing hole 10 and the breathing hole 13 is sealed, thus enabling water-filling to be completed easily.