What type of fitting must be installed at every right angle in water piping to facilitate cleaning and inspection?

The correct choice for facilitating cleaning and inspection at every right angle in water piping is an elbow fitting. Elbow fittings are specifically designed to create a 90-degree turn in a piping system, allowing for efficient redirection of flow while maintaining a smooth interior surface for easy cleaning and inspection. They are commonly used to connect pipes at angles, which is important for maintaining the integrity of the system and ensuring that there are no obstructions that could lead to blockages or pressure buildup.

For water piping systems, it is critical to ensure that fittings allow for thorough maintenance access to prevent sediment buildup and ensure water quality. Using elbow fittings at right angles helps achieve this objective effectively.

The other options, such as cross fittings and tees, are not specifically designed for right-angle turns and do not provide the same level of access for cleaning or inspection. Union fittings, while useful for joining two pieces of pipe, do not change the direction of the flow and therefore would not be installed at a right angle in a piping system.