Calculate Flow Rate

Level: Junior Apprentice

This resource will teach you how to calculate the flow rate in your system.

The flow rate is a measurement of how much water is flowing through your system at one time.

In general, your flow rate should cycle the volume of water in your fish tank through the grow bed at least once every hour.  This will help ensure that your fish are provided clean, oxygenated water and that nutrients are flowing to your nitrifying bacteria and plants.

To ensure your water is moving through your system at the correct rate, you need to calculate the flow rate.

You will need the following materials to calculate flow rate:

• 1-5 gallon bucket (or smaller depending on your tank size)
• Stop watch/timer
• Paper/pencil for recording

Procedure:

1. Locate a water source on your system that allows you to place the bucket in the flow of water- usually as it flows back to fish tank.
2. Time how long it takes to fill your bucket.
3. Repeat 3 times and average
4. Calculate the flow rate using formula below:

Flow Rate =Capacity/time      1 gallon bucket/ x minutes

Example of flow rate: 200 gallon fish tank / 1 hour  or  1 gallon bucket/ x 2minutes

Example of calculation:

If you have a 200 gallon fish tank, the pump needs to move 200 gallons per hour or every 60 minutes. Let’s say you are using a 1 gallon bucket. Use a timer to record how long it takes to fill the 1 gallon bucket. Repeat this 3 times and calculate an average time.

Trial 1=  1.25 minutes

Trail 2= 1.4 minutes

Trail 3=  1.5 minutes

Average: 1.43 minutes.   One gallon took 1.43 minutes.  Thus, to move 200 gallons would take 286 minutes (1.43 x 200). This is over an hour, so it is too slow and you need to turn up the flow on your pump.  Read the manufacturer’s directions and repeat your calculation and adjustments until you achieve the 200 gallons/hour flow rate.    For more practice on calculating flow rate, click here.

This information is provided by Sweet Water Foundation.

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