How To Shut Off Your Water Mains Valve In An Emergency

In a plumbing emergency, minutes matter. Knowing how to shut off your home’s water mains supply is the difference between a quick mop-up and thousands of dollars in restoration costs. Here is everything you need to know to find and kill the water flow before the damage spreads!

Why The Shut-Off Valve Is Your Best Friend In A Plumbing Emergency

In a standard home, water is delivered under significant pressure, usually between 350–500 kPa (40 and 60 PSI) for modern homes built after the 1990s. This means if a pipe bursts, it can dump litres and litres of water into your home in a very short space of time.

By the time you find your phone, search for a plumber, and wait for them to arrive, your carpets, drywall, and electrical systems could be unsalvageable. The mains shut-off valve is your very valuable “kill switch.” It stops the flow of water from even entering the home, aiding in reducing the amount of water and potential disaster into a manageable repair.

Where Is My Mains Water Shut-Off Valve?

Depending on when your home was built, your valve could be hiding in several different places. Here is a treasure map for the most common locations for NZ homes:

• Inside A Perimeter Wall. Most water lines enter the house through the side nearest the street. Check the interior of your walls and look for a small “access panel” on the wall or low down near the floor. For homes not built on concrete flooring foundations, this might mean investigating the crawlspace under the house. Pro Tip: If your valve is in a hard-to-reach crawlspace, consider hiring a plumber to relocate it to a more accessible interior utility closet or garage.
• The Utility Closet (hot water cylinder storage area). In many modern builds, the main line comes up through the floor in the same closet that houses your water heater or hot water cylinder. Pro Tip: Be careful what taps you turn off in the hot water cylinder cupboard as this may impact your hot water cylinder if you continue to use hot water from the tap and the water levels get too low.
• The Curb Box. In some instances, the water mains valve is located outside the property in a “curb box.” This is a concrete or plastic box buried in the ground near the beginning of your driveway or on the road edge. Pro Tip: These boxes often become slightly buried or overgrown with grass, you may need to poke around a bit to find them.

How Do I Turn Off The Valve?

Identifying and operating your mains water valve is just as important as knowing where it is! Not all valves are created equal here in NZ. You likely have one of the two following types:

The Ball Valve (modern lever style)

The ball valve features a heavy-duty handle that rotates. Inside the pipe is a ball with a hole through the centre. When the handle is “open,” the hole aligns with the pipe. These types of valves are extremely reliable and rarely leak.

How To Close A Ball Valve: Turn the handle 90 degrees. When the handle is perpendicular (forming a “T” shape) to the pipe, the water is 100% off.

The Gate Valve (older ‘wheel’ style)

Common in homes built before 1980, these look like a circular wheel or a garden hose handle. Turning the wheel lowers a metal “gate” inside the pipe to block the water. Gate valves are notorious for “seizing” or breaking if they haven’t been moved in years. Never force a gate valve. If it won’t budge, call a plumber to replace it.

How To Close A Gate Valve: Turn it clockwise (righty-tighty) until it stops. It may take several full rotations.

Secondary “Point-Of-Use” Shut-Offs

Sometimes, you don’t need to shut off the water to the whole house. If the leak is isolated to one fixture, use the point-of-use valves located near the leak.

• Toilets: Look for a small silver handle on the wall behind the toilet tank.
• Sinks: Look inside the cabinet beneath the sink. There should be two valves (one for hot, one for cold).
• Washing Machines: Check behind the machine or in the nearby tub. There are usually two levers or “faucets” where the hoses connect.
• Dishwashers: Often share the hot water shut-off located under the kitchen sink.

What To Do After You Shut Off The Water

Shutting the valve stops the new water from coming in, but there is still likely a lot of water sitting in your pipes throughout the house. Here are some quick tips for dealing with the residual water.

• Bleed The Lines: Go to the lowest level of your home and turn on the faucets or outside tap. This allows the water remaining in the vertical pipes to drain out.
• Turn Off The Hot Water Heater: If you are shutting off the main water for an extended period, turn off the power to your water heater. If the tank drains and the heating elements stay on, it can burn out the unit.
• Document The Damage: Before you start cleaning up, it is a good idea for insurance purposes to take photos and videos of the situation.
• Dry It Out: Use fans, water vacuums and dehumidifiers immediately to help dry the area as fast as possible. Mould can begin to grow within 24–48 hours.

What About Maintenance?

Plumbing valves are prone to seizing up because they are not used very frequently. Once a year (maybe when you change your smoke detector batteries), find your mains water valve and turn it off and back on again. If you notice any “crusting” (green or white powder) around the valve stem, this can be a sign of a slow leak. Call a plumber – it’s better to replace a $50 valve now than a $5,000 floor later!

Once you have correctly located your water mains valve it is a good idea to hang a bright luggage tag or a piece of coloured tape on it. In a dark, or when panicking in an emergency, you don’t want to be guessing which handle is the right one!

Don’t wait for a water crisis, knowing where your water mains valve is located is going to come in handy one day. We recommend that every member of the household knows where this valve is and how to operate it. Need a plumber now? Call Whitehead Plumbing & Gas for all your plumbing needs, we serve Christchurch and the greater Canterbury region.