For each bedroom beyond 4, how many gallons must be added to the minimum septic tank size?

The requirement to add 250 gallons to the minimum septic tank size for each bedroom beyond four is in line with the standards set for septic system design in West Virginia. This addition is necessary because each additional bedroom represents an increase in wastewater flow that the septic system must be capable of handling.

Specifically, the design criteria take into account that bedrooms typically correlate with the potential number of occupants in a home, and thereby affect the volume of wastewater produced. By mandating the addition of 250 gallons for every extra bedroom, the regulations ensure that the septic tank can adequately accommodate the increased demand without risking failure or contamination issues. This threshold helps maintain efficient and effective operation of the septic system, preventing potential problems related to residential wastewater treatment.

The other options do not align with the established regulation for septic tank sizing in relation to additional bedrooms and would not provide sufficient capacity to handle the resultant increase in wastewater.