**Foul Runoff ** can only be defined in Foul phases.

### Calculations

The resulting flow from the foul runoff is made up of three parts: Industrial flow runoff from the catchment area, Domestic flow runoff from the catchment area, and Foul flow from dwellings.

**Resulting Flow = Industrial flow rate + Domestic flow rate + flow rate from either Discharge Unit or Main Drainage.**

The flow from the industrial portion of the development is calculated by:

Industrial flow rate = Catchment Area x Industrial Peak Flow Factor x Industrial Flow

The flow from the domestic portion of the development is calculated by:

Domestic flow rate = Catchment Area x Domestic Peak Flow Factor x Domestic Flow

Foul flow from dwellings can be calculated using either the Discharge Unit method or the Main Drainage method.

Discharge Unit foul flow calculation:

Foul flow rate = SQRT( Total Discharge Units) * Frequency Factor

Main Drainage foul flow calculation:

Foul flow rate = (Flow Per Dwelling * Number of Dwellings) / 86400

**Industrial Flow (checkbox)** - Check to include industrial flow.

**Industrial Flow (textbox)** - The amount of industrial flow per unit area.

**Industrial Peak Flow Factor **- A factor to apply to the industrial flow to account for the peak flow.

**Domestic Flow (checkbox)** - Check to include domestic flow.

** Domestic Flow (textbox)** - The amount of domestic flow per unit area.

** Domestic Peak Flow Factor **- A factor to apply to the domestic flow to account for the peak flow.

**Calculation Method ** - The method used to calculate flow. Available options are Discharge Unit and Main Drainage.

**Discharge Unit**

**Total Discharge Units** - The total of all discharge units. Editable manually or via the Total Discharge Units Calculator.

**Frequency Factor **- Factor applied in calculating flow.

**Main Discharge**

**Flow per Dwelling **- The total flow for a single dwelling. Editable manually or via the Flow per Dwelling Calculator.

**Number of Dwellings **- The total number of dwellings.

**Resulting Flow Rate** - The total flow calculated.