Enter the well diameter and the depth of water in the well into the calculator to determine the purge volume. The purge volume is the amount of water that needs to be removed from a well to ensure that the water being tested is representative of the water in the aquifer.
Purge Volume Formula
The following formula is used to calculate the purge volume.
PV = π * (D/2)^2 * (DW * 12) / 231
Variables:
- PV is the purge volume (gallons)
- D is the well diameter (inches)
- DW is the depth of water in the well (feet)
To calculate the purge volume, use the formula above where the well diameter is halved to find the radius, squared, and then multiplied by the depth of water in the well (converted to inches) and π. The result is then divided by 231 to convert cubic inches to gallons.
What is Purge Volume?
Purge volume is the volume of water that must be removed from a well before sampling to ensure that the water sample is not contaminated by stagnant water and is representative of the aquifer’s water. This is a critical step in obtaining accurate water quality measurements, especially for environmental monitoring and assessment.
How to Calculate Purge Volume?
The following steps outline how to calculate the Purge Volume.
- First, measure the well diameter (D) in inches.
- Next, measure the depth of water in the well (DW) in feet.
- Use the formula PV = π * (D/2)^2 * (DW * 12) / 231 to calculate the purge volume.
- Finally, calculate the Purge Volume (PV) in gallons.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Well diameter (D) = 6 inches
Depth of water in the well (DW) = 100 feet
