It shouldn't be necessary to turn off the water to the entire house just to fix a leaky faucet, but that's exactly what many homeowners must do. Why? Because they don't have individual shutoff valves installed under every sink. If you're facing the same situation, consider putting a valve on every hot- and cold-water supply tube. The valves will not only allow you to shut off the water to one sink without disrupting the flow to others but they'll also provide a quick way to turn off the water in the event of a flood caused by, for instance, a cracked fitting or ruptured supply tube. The good news is that adding compression shutoff valves to an existing sink is a simple, straightforward job that most homeowners can handle. In most cases you won't even need to replace the supply tubes that run from the valves to the faucet. However, if the tubes are corroded or kinked, replace them with braided stainless-steel supply lines (about $5 each). Standard compression valves cost about $7 each.