Why would a Hayward pool pump run but make loud noise after it is switched on not water?

There are a few reasons why a Hayward pool pump might run but make a loud noise after it is switched on without water.

* Air in the pump. If there is air trapped in the pump, it can cause the pump to cavitate, which is a condition that occurs when the pump impeller spins so fast that it creates a vacuum and causes the water to vaporize. Cavitation can cause the pump to make a loud noise and can also damage the pump.

* Worn bearings. Worn bearings can also cause the pump to make a loud noise. This is because the bearings are responsible for reducing friction between the moving parts of the pump, and when they are worn, they can no longer do this effectively.

* Damaged impeller. A damaged impeller can also cause the pump to make a loud noise. This is because the impeller is responsible for creating the pressure that moves the water through the pump, and when it is damaged, it can no longer do this effectively.

If your Hayward pool pump is making a loud noise after it is switched on, it is important to turn it off immediately and call a qualified pool technician to diagnose the problem.