I would like to know if it is common practice to loosen the bolts for the water pump to tilt the pump for replacing the timing belt

 

For what purpose? Relieve tension on the belt? Remove the tensioner/idler pulley to accomplish this. You should replace the tensioner as well, since they are known to fail either before the belt, or around the same time, usually the former. You could spend all that time doing the belt, only for the tensioner to go out a few months later and causing valve damage. It's worth replacing the water pump while you're in there since you can pick one up for $40-60, cheap insurance.