Tapping is the process of connecting lateral lines and service lines to mains or other water lines. Work crews should be prepared to perform the tap as quickly and efficiently as possible. 

These questions and answers are from the book Introduction to Water Distribution, Principles and Practices of Water Supply Operations, Volume 3, American Water Works Association (AWWA), Denver, Colorado, 1986, ISBN 0-89867-188-4. 

Question 1:  What is the purpose of tapping?
Answer:  To connect lateral lines or service lines to water mains.

Question 2:  What is the difference between a wet and dry tap?
Answer:  A wet tap is made with the water main under pressure; a dry tap is made with the water main shut off. Usually, dry taps are made during the installation of a main. Wet tapping is the most common procedure to connect lines.

Question 3:  What are two advantages of wet taps?
Answer:  (1) Water service does not need to be interrupted and (2) there is less chance of contamination.

Question 4:  What is a corporation stop?
Answer:  The fitting used to connect small-diameter (2 inch or smaller) service lines to a water main is called a corporation stop.  It is generally a brass shut-off valve, threaded on both ends and inserted into a main to connect the service line.

Question 5:  When is a service clamp or saddle used?
Answer:  When the pipe wall is too thin or too soft or directly tapping into the main is not practical, a service clamp or saddle is used to install a corporation stop. The service clamp is attached directly around the main and the corporation stop is then threaded into the service clamp instead of the pipe wall.

Question 6:  What is the most common type of inlet thread on a corporation stop and what is the major advantage of this type of thread?
Answer:  The standard AWWA thread is most common used on the inlet end of the corporation stop. This is also known as the Mueller thread, the corporation cock or corporation stop thread.  The larger diameter and steeper taper of the AWWA thread has the advantage of greater strength and less wedging under pressure.

Question 7:  List three factors that determine the type of corporation stop to be used in a given installation.
Answer:  (1) Service line material, (2) service line diameter, (3) size and type of main, (4) use of service clamp or direct insertion and (5) type of connection to service line.

Question 8:  Name two methods of connecting laterals to mains.
Answer:  (1)  Tee connections and (2) tapping sleeve. Because water service must be interrupted to install tee connections, these are commonly installed when the main must be shut down for some reason. Shutting down the main creates water loss, contamination and possible complaints of dirty water. The use of drilling machines to connect lateral lines (3 inches or greater) reduces the problems associated with interrupting water service. The connection to the main is made with a tapping sleeve and a tapping valve is used instead of the corporation stop.

Question 9:  What is the most common connection size for residential service lines?
Answer:  A three-fourths inch connection is generally the standard requirement for residential service.

Question 10:  List three important precautions to take when using a tapping machine.
Answer:  (1) Make sure the bit is clean and sharp, (2) check to determine that the cutting tool is lubricated, (3) do not force the bit through the pipe wall.

Question 11:  What kind of information should be recorded regarding service taps?
Answer:  The water system should retain information on (1) name of the contractor or foreman in charge of the job, (2) date of installation, (3) exact location of the tap, (4) tap size and (5) main size.

Question 12:  What safety hazard exists when making a wet tap?
Answer:  (1) The pressure in the main can blow out a poorly installed corporation stop, (2) plastic pipe may split abruptly, (3) the trench may suddenly become flooded or collapse.