Finding the Main Water Shutoff Valve
After the water passes through the three city-installed valves, it comes to what is known as the main shutoff valve in your home. This is the valve that you need to be able to locate in an emergency. Find it before an emergency occurs so, when you're in a pinch, you know where it is. This valve is usually in the basement or on an outside wall in a utility area of the house. The main shutoff valve allows a full flow of water through the pipe when it’s open. Turning off this valve (by turning it clockwise) cuts off the water supply to the entire house.
The main shutoff valve in your house probably has one of two designs:
Gate valve: Gate valves are very reliable and last for years, but they become difficult to turn after not being turned for years. If you haven’t closed the main shutoff valve since you moved into your house, do it now. Better to find out that you can’t turn it with your bare hands now than to wait until you’re standing in 6 inches of water.
Ball valve: Houses with plastic or copper main water pipes leading into the house may have a full-flow ball valve. This valve is open when the handle is aligned with the pipe. To close it, turn the handle clockwise 1/4 turn so that it’s at a right angle to the pipe.
The main valve is the one to stop most plumbing catastrophes, such as a burst pipe. Make sure that everyone in the household knows where this valve is located and knows how to turn it off. Turning the handle clockwise closes the valve. You need to turn the handle several turns to fully close a gate valve.
After you’ve closed and opened the valve, it may start to leak a bit around the valve stem. The stem of the valve is held in place with a packing nut. Tighten this nut just enough to stop the leak. Don’t overtighten it or the valve is difficult to turn again. (If you need a cheat sheet to remember which way to turn the control, use a label or tag with the simple reminder: Right off with an arrow pointing right, for example.)
Any time you shut off the water and allow the pipes to drain, unscrew the aerators (small screens) on the ends of all faucets before you turn the water back on. Doing so keeps the small particles of scale that may shake loose from inside the pipes from clogging the small holes in these units.