Calculate hydraulic detention time (HRT) from tank volume and flow rate using T = V / Q.
Choose whether to enter tank volume directly in gallons, or calculate it from tank dimensions (length x width x depth) in feet. Dimensions are converted using 7.48 gal/ft3.
The total liquid volume of the tank or basin in gallons. This is the effective volume available for water treatment contact time.
gallons
ft
ft
The effective water depth in the tank, not the total tank height. Measure from the floor to the water surface or weir level.
ft
The rate of water flowing through the tank in gallons per minute (GPM). Common conversions: 1 MGD = 694.4 GPM; 1 GPM = 1,440 GPD.
GPM
Results
Tank Volume-gallons
Detention Time-minutes
Detention Time-hours
Turnovers per Day-per day
Daily Flow Volume-MGD
Formulas & References
Detention Time (min) = Volume (gal) / Flow Rate (GPM)
Volume (gal) = Length (ft) x Width (ft) x Depth (ft) x 7.48 gal/ft3
Turnovers/day = 1,440 min/day / Detention Time (min)
MGD = GPM x 1,440 min/day / 1,000,000
Reference: AWWA Water Treatment Plant Design; EPA Water Treatment Manual; Sacramento State Operator Certification Program