The monthly flow charge for residential sewer charges shall be the average water usage (metered water) for the months of November, December, January and February. This average shall be used to calculate sewer flow charges throughout the twelve (12) months of the year and shall be recalculated each year for a new average. Households who have not established a true winter average for the four (4) months mentioned above shall be assigned an average based on the number of individuals who reside in the house. This average shall be computed at fifty (50) gallons of metered water per day per individual. Commercial businesses will be based upon actual water usage (metered water). (Res. 337, 5-10-2004, eff. retroactive to 5-1-2004)