When a back water valve is installed in a subsoil drain system, it is required to be in a minimum ______________ inch diameter manhole.

When a backwater valve is installed in a subsoil drain system, it must be situated within a manhole that has a minimum diameter of 48 inches. This requirement is crucial for several reasons.

Firstly, the larger diameter allows sufficient space for maintenance and servicing of the backwater valve. Proper access is essential for inspections, cleaning, and repairs, ensuring that the valve operates effectively over time and minimizes the risk of system failure.

Secondly, installing the valve in a adequately sized manhole helps facilitate the flow of water and reduces the risk of blockages. A 48-inch diameter provides the necessary clearance for water flow, which can be particularly important in high-volume drainage scenarios.

Additionally, local codes and standards often dictate the dimensions of manholes for various applications, and opting for a manhole with a diameter of 48 inches ensures compliance with these regulations. Such adherence supports the overall integrity and functionality of drainage systems, contributing to effective water management practices.

Thus, choosing a 48-inch diameter manhole is not just a preference but a necessity to accommodate the proper installation and long-term performance of the backwater valve in a subsoil drain system.