When Should I Leave the Faucets Dripping?

Temperature and Exposure

The Institute for Home and Business Safety recommends that homeowners in the South leave faucets dripping overnight when the outside temperature drops below 20 degrees Fahrenheit. Due to the infrequency of below-freezing temperatures in the southern portions of the United States, builders will often leave plumbing in crawlspaces and attics exposed. While water freezes at 32 degrees Fahrenheit, the ambient temperature in a crawlspace or attic is usually several degrees above the outside temperature. This leaves a small safety margin for un-insulated southern plumbing. Faucets connected to pipes directly exposed to the environment should be left dripping when the temperature drops below freezing. In colder parts of the United States where freezing temperatures are more common, plumbing tends to be better insulated and is usually safe from freezing until the temperature approaches zero, at which point it's time to leave a faucet dripping.

Houses with drainage plumbing in poorly insulated crawlspaces can be an exception to this rule. The small amount of water dripping from a faucet may not be enough to prevent freezing in "P" traps located under toilets, showers and tubs. Once the drains are plugged with ice, the water escaping the faucet may overflow the sink or tub. The best bet is to insulate the drainage pipes prior to a freeze. If this is not possible, place a 100-watt incandescent light bulb in the crawl space close to but not touching the drain pipes. Then, leave the faucet above dripping.

A small amount of running water, a stream no larger than the diameter of a pencil lead, will prevent a pipe from freezing under most conditions. In milder conditions, a steady drip will save water and prevent plumbing damage.

The sound of a dripping faucet seems to be magnified during the night when the house is quiet. Water bouncing off the bottom of a sink or tub doesn't need to disturb your rest. Tie a string long enough to reach the bottom of the sink or tub around the opening of the faucet. The string will give the water a path to follow and slow the water's progress enough to eliminate the dripping sound. Alternatively, a thick washcloth placed underneath the faucet may work as effectively.