The first step in diagnosing whether or not your shower needs a new drain is to check the condition of the existing drain. If the existing drain is cracked or chipped, then it is likely that it will need to be replaced. If the existing drain is leaking, then it is also likely that it will need to be replaced. You should also check for any blockages in the pipes leading to the existing drain. These blockages can cause water to back up into your bathroom, which can cause damage to your bathroom fixtures and floors.