If a pipe bursts in your home or springs a leak, knowing where the main water shut-off valve is located and how to turn it off can save money and the headache of having to clean and repair the water damage. The main water shut-off valve can be outside or inside the home, and its location varies depending on the age of the home and local building codes. The easiest way to find your main water shut-off valve is by knowing whether the home was constructed on a slab, basement or crawl space.