1.Horizontal in the open pump before the start of the filling is not enough water, sometimes looks like the water has been poured from the vent overflow, but did not turn the pump shaft to the air completely discharged, resulting in a little air left in the water pipe or pump body.
2.The water inlet pipe above the level of the application of reverse flow direction, fell more than 0.5% slope and horizontal pump in the open end of the contact, open import pump is connected to the highest level, not completely. If the upward tilt, will be retained within the inlet air, reduce the pump in the vacuum pipe and the horizontal, the impact of water.
3.Horizontal pump filler has been used for long-term wear or packing pressed too loose, discharge gap caused by the large amounts of water from filling with the shaft sleeve, the result is the outside air from the inside of the gap into the pump in the open, affected the water.
4.Because of the long-term potential of the water inlet pipe, pipe wall corrosion appeared holes, the water continued to decline after the opening of the pump, when these holes exposed, the air from the hole into the water inlet pipe.
5.The water inlet pipe bend pipe is in the crack, the water inlet pipe and the horizontal open pump connection in the small gap, it is possible to make the air into the water inlet pipe.
