How to Connect Faucets with Supply Tubes

Supply lines are flexible tubes that connect your water supply to your plumbing or appliance fixture. They’re available in different sizes. The size refers to the diameter of the fittings on either end of the tube, so check your fixtures to see what size you need. The fittings typically come in 1/4-, 3/8-, and 1/2-inch diameters. These measurements can be the same or different on either end of the tube. 

Tip: Confirm whether you need male or female connectors as well. A male connector fits into fixtures and a female connector fits over fixtures.

Under the sink, locate the shut-off valve for the hot and cold water lines. Turn each valve in a clockwise direction to cut off the water. Test that the water is turned off by turning on your faucet. If no water comes out, you have turned off your valves. 

If the shut-off valve is stuck in the open position, locate the nut behind the valve handle and slightly loosen it with a wrench. This relieves the valve pressure and makes it easier to turn. Retighten the packing nut to prevent leaks.

Before installing new supply lines or a new faucet, remove the old faucet and supply tubes. 

• Use a wrench to disconnect the supply tubes.
• Unscrew the retaining nuts that hold the faucet in place. The nuts can be tricky to access. Try using a specialized tool called a basin wrench that can reach into cramped areas like under sinks.
• If the nuts are overtightened or damaged, you may need to cut them. Use a rotary tool to cut through one side. Pry the nut away with a screwdriver.
• If you are replacing the faucet, pull the old faucet out from above the sink.
• Remove the old hardware from below the sink.

Skip this step if your new faucet comes with supply tubes attached that are the correct length, size and type.

To attach the supply tubes to the faucet:

• Wrap plumber's tape around the threads of the faucet's male hot and cold fittings to prevent leaks.
• Label the hot and cold tubes so you know which one is which
• Match the hot tap attachment to the hot water tube and the cold water tap attachment to the cold water tube.
• Attach the connectors to the fittings with a wrench or basin wrench.
• You should now have two tubes hanging down from the faucet attachment.

Skip this step if you are not installing a new faucet.

To install the faucet, run the threaded tailpieces and supply connectors through the pre-drilled holes in the sink or the countertop. Apply a bead of silicone caulk along the underside edge of the faucet to help create a seal that keeps water out and prevents corrosion.

Underneath the sink, place a rubber gasket, a retainer ring and a nut onto the threaded tailpieces to secure the faucet to the sink. Tighten the nut with your fingers and give it a final quarter-turn with a basin wrench or pliers. Take care not to overtighten the nut. It can create a crack in the countertop.

Wrap the male threads with plumber's tape to ensure a good seal. Connect the hot and cold tubes you labeled earlier to the hot and cold valves. Hand-tighten the connections to start, then fully tighten them by using two adjustable wrenches or a wrench and a pair of pliers.

Before you turn your water back on, remove the aerator from the end of the faucet by unscrewing it in a clockwise direction. The aerator is the tip of the faucet that holds screens. Working on plumbing in your home can cause minerals and other debris lodged inside pipes and valves to come loose and clog the aerator. 

With the aerator removed, turn the shutoff valves counterclockwise to turn the water back on. Turn on the faucet and let it run for two or three minutes. 

Tip: If you can’t remove the aerator, remove the entire nozzle head for a few minutes while you let the water run.

While the water is running and flushing the lines, check for leaks in the new installation. Look under the sink. Use a flashlight for best visibility. To check for leaky connections, wipe the joints with some tissue. Even a small leak will create a visible wet spot. If you notice any water, re-tighten the connections and run the water again to make sure there are no leaks. After you have flushed the lines and checked for leaks, turn the tap off and screw the aerator back on.