What is the acceptable slope tolerance for the bottom of a raised filter bed mantle?

The acceptable slope tolerance for the bottom of a raised filter bed mantle is critical for ensuring proper wastewater treatment and effective drainage. A slope that is too steep could lead to uneven distribution of effluent, which can overload certain areas of the filter bed while leaving others dry, ultimately resulting in system failure.

A tolerance of plus or minus 1 inch strikes a balance that allows for some variability in the installation process while still adhering to the necessary guidelines for effective function. This range accounts for minor discrepancies that may occur during installation due to site conditions or human error, without compromising the overall performance of the septic system.

Establishing a tolerance of different measurements, such as those presented in the other options, could lead to either excessive or insufficient slope, which isn't conducive to the designed flow dynamics required in septic systems. Thus, the plus or minus 1-inch tolerance is the most suitable choice for ensuring optimal functioning of the raised filter bed mantle.