For traditional faucets, the knob to the right of the spout controls cold water, while the knob to the left controls hot water. With a single handle faucet, both hot and cold water are controlled by the same handle. The handle is shifted to the right controlling cold water, and shifted to the left controlling hot water. But both types of faucets are supplied by two supply lines located underneath the sink. Switching the hot to cold is a simple task, requiring only basic plumbing skill. You also can adjust the mixture of hot and cold water the faucet dispenses.

Locate the hot and cold cutoff valves underneath the sink. They are chrome-colored knobs against the back wall under the sink, and each has a thin plastic or metal tube that runs up to the faucet.

Turn each knob counterclockwise to turn off the water supply. Turn on the faucet to make sure the water supply is off before removing the supply line

Disconnect the supply lines by twisting the nut that attaches the supply line to the cutoff valve counterclockwise with a wrench.

Attach the supply line that had been on the left (hot) cutoff valve to the right cutoff valve, and tighten it by twisting it clockwise. Attach the remaining supply line to the remaining cutoff valve, and tighten it.

Turn on both cutoff valves, and watch for leaks. Shut off the leaking valve, remove the nut and retighten to stop a leak.

Shift the handle to the right. You should feel hot water. Shift the handle to the left for cold water.

Remove the single handle. Depending on the faucet, you either use a flat screwdriver to pry off the small plastic cover concealing the retaining screw, or remove the retaining screw from underneath the handle.

Adjust the water mixture. Some faucets have two small adjustment screws underneath the handle. The screw on the left controls hot water, while the screw on the right controls cold water. To increase water temperature, either turn the hot water screw counterclockwise or turn the cold water screw clockwise. To decrease water temperature, either turn the hot water screw clockwise or turn the cold water screw counterclockwise. Other faucets have either small plastic nubs that you turn by hand or with pliers to adjust the hot/cold mixture or a temperature adjustment ring you rotate clockwise to adjust the water temperature.

Replace the handle and tighten the retaining screw and any cover you removed.