What type of fitting must be installed in the water piping connection at every right angle to assist in cleaning?

The correct type of fitting to be installed in the water piping connection at every right angle to assist in cleaning is a cross tee fitting. A cross tee fitting allows for multiple branches at a right angle while providing convenient access points for cleaning and maintenance. This type of fitting is particularly advantageous in plumbing systems where multiple lines intersect, as it enables easy cleaning and flushing of the system.

In contrast, elbow fittings are generally used to change the direction of a pipe, but they do not provide access for cleaning. Tee fittings connect three lines but may not facilitate cleaning as effectively as a cross tee, particularly in complex piping systems. End cap fittings are used to close the end of a pipe, providing no access for cleaning. Therefore, the cross tee fitting is essential for effective maintenance in systems with numerous connections.