My problem is that all hot water outlets in the house make an air hammering sound when they are turned on then they proceed to pour water normally and then after a couple of minutes they start to make the sound again which goes on as long as u have it on

How long since you last flushed that heater? You could have some debris caught in the heat traps or valves at the outlet. Leav your main open, put a hose on the drain valve at the bottom and direct to a floor drain or sink. Open the valve for several minute until the wateris perfectly clear, then close. Shut down your main and open all faucets throughout the house and the go backl a drain the heater for about 2 minutes, this will help to reestablish air in the chanbers. Close the valve, close the faucets and slowly open the main all of the way. Now test each faucet, you may also need to remove any aerators and clear debris.