Whenever the weather gets really cold, you have the risk of frozen pipes and of those pipes bursting. There are things that you can do to help avoid having a burst water pipe, such as making sure that you leave a little water running through the pipes, wrapping the pipes in heat tape, or opening cabinet doors so that heat can get into pipes that are in an exterior wall. However, if your pipe does freeze and burst, you are going to need to have a plumber come in and repair it. So, what can you do until the plumber gets there?
Stop the Water
Before you call in the plumber, you need to make sure that you have done everything you can to limit the water damage. That means shutting the water off at the source. If possible, you need to turn off the water for your entire house. You should have a main shut-off point at your meter or at the incoming pipes in your cellar, basement, or crawl space. If you live in an apartment, you may not have access to that main water shut-off point, so you may need to call a maintenance man, property manager, or your landlord to handle that. If you can't get to that, then determine where the nearest valve for that pipe is, and try turning it off there. The sooner you can get the water turned off, the better off you are going to be because you are going to have less damage to clean up.
Find the Leak
If you can't see the burst pipe, only the water coming from it, you are going to have to track it down. Water is tricky; it may show up a distance away from the leak, depending on where the broken pipe is. There are things that you can do to help figure out where the leak is. One of them is that you can look for things like bubbly paint or wallpaper. If you can locate where the leak is, you can help the plumber because they aren't going to have to cut into as much wall to find the problem. If you see water running down your walls, you will want make sure that you check out your ceiling as well as your walls.
A burst water pipe can be a serious problem. You are going to need to have a plumber look for it, but there are things you can do to help make sure the damage isn't too bad. Contact a plumber for more info.