There are some things every homeowner should know, one of them is how to turn off the water to your house. Knowing this, and ensuring that the valve works, can prevent a small plumbing problem from becoming a complete disaster. If you have some kind of leak being able to turn off the water that prevents other parts of your house from damage. Replacing drywall and flooring can get very expensive very fast.
For most houses, the water enters at one point and if you have a basement it will likely come close to the floor. If you live in the north then it will have to be below the frost-line which in my area is at least 42″ deep. In my house, it comes in about 1′ off the floor.
In order for water valves to keep working they need to be cycled through on and off periodically. One word of caution, trying to turn off old plumbing can actually create problems. If it has become corroded then forcing it to turn can cause it to start leaking and then your problem just became worse. This means turning off the water at the street and replacing the valve. If you really know what you are doing and have the proper tool you can do this, but likely it means calling a plumber, and if you create this problem after hours then the price will be much higher.
The picture at the top is the main shut-off valve for my house. It is the ball valve type and is better than the gate valve type. Take a few minutes and find your main shut-off valve and assess it’s condition.