Calculations below are based on the DEP RSF Design Guidelines and best management practices developed by OMNI. These calculations can be downloaded as a text file and are included with the OMNI CAD Templates.
*Sand Filter Media = 38" depth <1% #200 sieve, 2mm to 4mm size
Average Daily Flow = 110 gpd per bedroom (per Title V)
Wastewater Strength (BOD5 for Residential) = 230 mg/L
*Recirculation Ratio Maximum 8:1 (variable - adjusted by operator)
*Recirculation Tank Size = 150% of Design Flow (per Title V)
1.5 x 330 = 495 (Minimum 1000 gallon tank)
*Sand Filter Loading Rate = 1150/BOD5
BOD5 = Septic effluent mg/L
1150 = Conversion factor
1150 / 230 mg/L = 5 gpd/ft2
Sand Filter Surface Area = (Flow gpd) / (Loading Rate gpd/ft2)
330 gpd / 5 gpd/sq. ft. = 66 sq. ft. Required
2 OMNI RSF Filter Modules Required
Recirculation Pump Size = Daily Flow x Recirculation Ratio + Back Flow
330 x 8 + 10 = 2,650 gpd
2,650 / 24hrs = 110 gal per hour (variable cycles - adjusted by operator)
Use Myers Model #ME40 or Equal (65 gallons/min @ 12 ft. Total Head)
*Sand Filter Module Setbacks = Same as Title V Septic Tank
*Is a constant and will not change for single-family designs
