Bathrooms get used every day and if you have a large family it can seem like the bath or shower is constantly running. It is quite common for a bathroom to spring a leak simply because of the amount of water that is being used and how often it is used. Often the first signs of a bathroom leak is water either puddled on the floor or water leaking though the ceiling below.
If you notice that you have a water leak you need to investigate where it is coming from as quickly as possible. If the leak is happening all the time and not just when the shower is run or the toilet flushed for example, then you need to find the stop tap and turn the water off. It may be that there is a leak in the pipes that supply the water to the bathroom.
If you have narrowed the leak down to a shower or bath then the first thing to check is the sealant around the edge. This is often silicon but over time it can wear away or become damaged. If this happens then water will easily run behind it and then leak down the walls through to the ceiling below. This is often an easy fix but you may want to get a professional in to ensure that it is sealed properly.