Don't let this be you!
It could be a burst supply line to the washing machine, an overflowing toilet, or any number of things: in the moment, it doesn't matter. As the water sprays and pools, all that matters is stopping it. Every second it continues adds toil and expense to the cleanup; allowed to go on for too long, the damage can be extreme. Thankfully, shutting off the water supply to a house or a specific fixture is usually really easy. Problem is, not enough homeowners (and certainly not many renters) know where to look!
Local Shut-Off Valves
Your plumbing fixtures likely have their own water supply shut-off valves. The most obvious is usually the toilet, which is a good thing - once you realize your flush didn't quite take and the water (along with everything else) in the bowl keeps rising, it's nice to be able to reach down and quickly diffuse the situation. Your sinks and dishwasher should have shut-offs in the cabinet or under the counter, and your water heater will have one as well. A FloodStop system can help prevent flooding from fixtures using a water-sensor and motorized ball-valve. When water is detected, the valve shuts off the fixture's water supply and sounds an alarm.
Main Shut-Off Valve
Plumbing problems, however, are not always so localized. When a pipe bursts, panic can quickly follow (if you're lucky enough to be home at the time). This is why it's so important to know where all of your shut-off valves are, not just the easy-to-find ones inside. Many homes have an exterior shut-off located near the perimeter of the house, often near the front-most outdoor faucet. If you aren't home, a remote controlled water shut-off system is a great way to maintain your peace of mind. Like the FloodStop, a sensor detects water caused by a leak or flood. Instead of shutting off the water supply to a single fixture, however, these automatically shut off your home's entire water supply.
As mentioned, the main shut-off is usually located on an outside wall of the home, but can also be in the basement or a utility room. Unlike the smaller valves that turn off water to fixtures, your main shut-off valve will usually be either a gate valve or a ball valve. Ball valves have one open and one closed position, but gate valves may take several turns to fully close or open. While gate valves can be reliable and last for years, they can also be difficult to turn - especially if they haven't been turned in a long time. If you have this type of valve, we recommend you try turning it ASAP. It's better to find out now that you need a wrench or other tool to operate it.
Water Meter Shut-Off
The main water shut-off will turn off water to the house, which can help if your leak or burst pipe is inside the home, but does nothing for leaking irrigation pipes. There are also times you may need to turn off the water to everything on the property to find or fix a problem. In addition to the local and main shut-off valves, the home's water meter box will also have a shut-off (or two: one on the customer/house side of the meter, one on the street-side). Depending on your climate and utility company's preferences, the water meter might be located in a basement or in a box underground somewhere between the house and sidewalk. Generally, if you live in a climate that experiences freezing winters, your water meter is likely in your basement or a similar area of the home.
Sometimes, your water meter may actually be located on your neighbor's property. In these cases, it's definitely a good idea for you and your neighbor to know beforehand. Make sure you're both clear as to whose meter is whose (they're normally positioned side-by-side: yours should be the one closest to your property), and that you're both comfortable with the occasional visit to the meter box. Should there be any confusion or resistance, your utility company should be able to help clear things up.
The water meter shut-off valve usually has an arrow indicating the direction of water flow. The valve will sometimes have a handle that can be turned by hand, while others require the use of a water meter key. You may be able to use a wrench and screwdriver in place of the key. All you should need to do is turn the valve handle clockwise to shut off the water flow to your home. Excessive force should not be necessary. If the valve handle is difficult to turn, contact your local utility company - you do not want to be responsible for any damage to your water meter.
Stopping a blockage or burst pipe from turning into a catastrophe is one of the most important things you can do to protect your home. Know where your shut-offs are, and make sure everyone else in the house does as well. You may not be able to save the pipes, but you will save time, money and hassle.