PEX is a flexible tubing option that is used to connect plumbing fixtures in the home. The material is soft enough to cut if needed, and bends to fit even the tightest install areas, such as under sinks. In addition, PEX is less expensive than most other metal pipe options. When connecting PEX tubing to a faucet, you must make sure the coupler is tight enough to prevent water leakage.
Look at the end of the PEX tubing and make sure that the cut edge is straight and smooth instead of jagged or slanted. If necessary, cut through the end of the tubing with a sharp utility knife to clean up the cut.
Slide a plastic PEX coupler over the cut end of the tube. Install the large round section first, followed by the smaller plastic nut, which has a much tighter fit. When purchasing the coupler, get the same-diameter coupler as the PEX tubing.
Locate the proper connection opening at the bottom of the faucet, using the faucet's instruction manual. There are typically two openings, one for hot water and one for cold water. Push the cut end of the tube into the faucet opening until it will not move any farther.
Slide the plastic nut down as close to the faucet as possible, and then slide the larger plastic coupler over it. Turn the plastic coupler clockwise until it no longer turns. Next, place a wrench around it and turn it clockwise two more times to ensure a tight seal.
Turn on the water supply valve. The water supply valve is typically located on the wall near the piping. Turn on the faucet at the top of the sink and examine the PEX tubing for leaks. If leaks are present, turn the coupler an additional half-turn clockwise.