Fitting pipes together has traditionally been a fairly technical procedure that involves a process known as "sweating the pipes," which requires using a propane torch and should be done only by a professional. However, compression fittings such as tees can be used to make joints between pipes and make repairs in the line of a pipe. Brass and PVC compression fittings are available in various sizes. A tee fitting is joins one pipe at a 90-degree angle to the middle of another pipe, creating a three-way junction.
Turn off the water supply to the pipe you will be joining to. If a cut-off valve is not located on the line, use a wrench or plumber's pliers to turn the water off at the meter.
Layout the pipe to determine where the joint needs to be made. Mark the pipe you will be joining to at the place where the tee fitting will go with a marker.
Cut the pipe you will be joining the new pipe to with a twisting tube cutter for copper pipe or a ratcheting cutter for PVC. Cut a half-inch piece from the original pipe to provide space for the fitting and nice smooth ends for proper seating of the compression fitting. Cut the end of the pipe you are joining to the original pipe to length. Make the cut smooth to ensure a good fit.
Separate the compression nuts and rings from the tee. One nut is at each opening---three nuts total. The compression rings are the short cylindrical bands inside the nut. Remove them by twisting counterclockwise. In brass fittings, the rings are copper, and in PVC fittings, the rings are typically clear or black nylon plastic.
Fit one compression nut onto one end of the original pipe, with the threaded side facing the cut end, and slide it up several inches. Slide a compression ring onto the same pipe. The tee fitting will have two openings straight across from each other, creating the top of the tee, and one at 90 degrees to them. Place the pipe with the nut and ring into one side of the top of the tee.
Push the nut down to the fitting, with the compression ring between the nut and the fitting. Twist the nut onto the fitting by turning clockwise until it is snug. Use plumbers pliers to turn it one and a half turns more. Repeat by inserting the other side of the top of the tee fitting into the remaining end of the original pipe. Be careful not to over-tighten the nuts.
Place a nut and compression ring on the end of the intersecting pipe, and insert it into the remaining opening of the tee. Twist the nut tight as before.
Take a piece of the pipe you are working with to the hardware store to help determine which fitting you need.