What is the required percolation test standard for a DIS?

The required percolation test standard for a Designated Intermittent System (DIS) in Illinois is that it must not exceed 270 minutes for a 6-inch fall. This standard is critical because it establishes a maximum allowable rate of absorption for septic systems, ensuring that effluent percolates adequately through the soil and is treated properly before reaching groundwater or surface water.

When the percolation rate is too slow or exceeds this threshold, it can indicate that the soil may not be suitable for proper wastewater treatment, leading to potential system failures or environmental health issues. Meeting this standard helps maintain safe and effective waste management practices.

The other choices reflect percolation rates that would imply a faster absorption than is permissible for proper function, which could compromise the health and safety standards required for septic systems in Illinois.