What is the FF formula for a house with more than 3 bedrooms?

The FF formula for a house with more than three bedrooms provides a way to calculate the flow factor, which helps determine the septic system's capacity needed for proper wastewater treatment. In the correct formula, the total number of bedrooms is taken into account, with a set flow rate for the first three bedrooms and a different adjusted rate for any additional bedrooms.

For a house with up to three bedrooms, the flow rate is typically calculated at 150 gallons per day (GPD) per bedroom. Therefore, for the first three bedrooms, the calculation is straightforward: 3 bedrooms times 150 GPD gives 450 GPD. However, when there are more than three bedrooms, it’s important to add a reasonable adjustment for those extra bedrooms.

The correct formula incorporates the flow rate for the first three bedrooms and adds a reduced flow rate for each additional bedroom. Specifically, after the initial three bedrooms, the additional bedrooms contribute 75 GPD each. This is why the formula breaks down into two parts: the base calculation for the first three bedrooms and the adjusted calculation for any bedrooms over the initial three.

In summary, the formula provides a comprehensive method for estimating the septic system's requirements based on the number of bedrooms. This two-tiered approach ensures