How to Stop Water When Installing a New Sink

At the Sink

• If you're lucky, the original plumber -- or someone along the way -- installed water shutoff valves on the water lines directly beneath the sink. These make replacing a sink very easy. All you have to do is turn off the water valves, switch out the sinks, attach the plumbing and turn on the valves. In the meantime, everything else in the house still has a water supply. To find the shutoff valves, look for a knob on both the hot and cold water lines that feed into the faucet. Turn them clockwise, then test to ensure the water is off.

At the Heater

• If the shutoff valve is not at the fixture, look at the next most common spot: the water heater. The water heater has two sets of metal pipes -- one carrying cold water into the unit; another carrying hot water away to the rest of the house. Turn the knob on the outbound pipe clockwise to stop the hot water supply instantly. Alternatively, if there isn't a shutoff valve on the outbound pipe, turn off the incoming pipe's shutoff valve, then run the hot water in a sink to drain the hot water completely.

At the Main

• Of course, draining the hot water heater and preventing it from refilling only solves half of the problem -- the sink's hot water supply. To turn off the cold water supply, look for a separate cold water pipe that runs beside, but bypasses, the heater. Instead, it has a branch running to the hot water heater. If you're in luck, this pipe is visible from the hot water heater and will have a shutoff valve on it. Alternatively, trace the cold water line from the heater back toward the main line coming into the home. At some point along the way, there will be a round, colored, somewhat knobby dial. Turn this shutoff valve to stop the cold water, then check your sink to ensure it worked.

At a Manifold

• Near the water heater and along the main water supply line, you may also find a PEX manifold. A fairly new residential water-system method, manifold plumbing is nothing more than a control center, with hot and cold water feeds routed to individual fixtures. Find the main water supply line entering the manifold and look for the valve that stops the water into the manifold. Turn it off to eliminate water flow to both the hot water heater plus every fixture in the house. Alternatively, stop the specific manifold that routes cold water to the sink, then turn off the hot water heater as described.

At Your Meter

• When all else fails, find your water meter (assuming you have city water) and turn off the house water supply at that point. Your meter location will vary according to the climate and the placement your local water authority chooses. In warmer climates, you will usually find it in a buried box near the street and the end of the property line. In colder climates, it may be inside a basement. You may even find it on an exterior wall. Typically you will notice two separate shutoff valves -- one before the meter (the supply-side valve) and one after (the house-side valve). Turn the house-side valve to stop the water. Ensure the water is off before proceeding.