In which scenario is it necessary to have axial restraints for a horizontal drain pipe?

Axial restraints are important in plumbing systems to prevent movement that can lead to stress on the joints or offsets in the piping. In the scenario of a horizontal drain pipe at a 90-degree turn, axial restraints are necessary to control any potential axial movement that could occur due to changes in temperature or pressure fluctuations within the system.

When water flows through a pipe and encounters a bend, there can be a change in the flow dynamics, which can generate stress at the elbow joint. The axial restraints help to stabilize the pipe and mitigate any movement that could occur at the bend. This is crucial for maintaining the integrity of the joint and preventing leaks or failures over time.

While vertical suspensions, pressure testing, and flood hazard areas may also require specific considerations for pipe support and stabilization, they do not specifically necessitate axial restraints in the same way as the sharp directional change encountered at a 90-degree turn in a horizontal drain line, where the potential for movement is greatest.