Which formula represents detention time in a tank given volume in gallons and flow in gallons per day?

Which formula represents detention time in a tank given volume in gallons and flow in gallons per day?

• A. Volume divided by flow
• B. Volume x 24 / Flow
• C. (Volume x 24) / Flow
• D. Flow / Volume

Answer: (C)

Detention time tells you how long the water stays in the tank. It’s found by dividing the tank volume by the flow rate. Since the flow is given in gallons per day, that result is in days. If you want the time in hours, multiply by 24 hours per day. So the detention time in hours can be written as (volume ÷ flow) × 24, which is the same as (volume × 24) ÷ flow. That’s why the correct form is Volume × 24 ÷ Flow. For example, a 12,000-gallon tank with a flow of 1,500 gallons per day gives 12,000/1,500 = 8 days, or 8×24 = 192 hours.

Detention time tells you how long the water stays in the tank. It’s found by dividing the tank volume by the flow rate. Since the flow is given in gallons per day, that result is in days. If you want the time in hours, multiply by 24 hours per day. So the detention time in hours can be written as (volume ÷ flow) × 24, which is the same as (volume × 24) ÷ flow. That’s why the correct form is Volume × 24 ÷ Flow. For example, a 12,000-gallon tank with a flow of 1,500 gallons per day gives 12,000/1,500 = 8 days, or 8×24 = 192 hours.