How to Measure the Well Casing Diameter

Why do I need to know my well casing diameter?

Reason #1 To ensure your pump will fit down the well

RPS Water Pumps carries submersible pumps that are 3.85" in diameter, meaning you'll need at least a 4" casing, or a rare 3.5" casing, for the pump to fit down well. 

Reason #2 To size a well seal or well cap 

Every well will need to be covered in some way to prevent debris and animals from sneaking in (you don't want a dead rat in the well!). You'll choose between a well seal or a well cap.  

Measure with a Measuring Tape

You'll be measuring the ID (inside diameter) of the well casing. Place the metal tipped end of the tape on the inside of the casing, and measure to the inside edge of the opposite side. Write your number down! 

Residential wells commonly use 4,5, and 6 inch diameter casings. Older wells or agricultural wells use larger casings, 8,10, and 12 inch. 

Measure with a Piece of String 

Wrap a piece of string around the outside of the well casing. Mark where the two ends meet. Once you’re back in your shop, take out the tape measure and measure the length of the string to get the circumference of the well. Divide the circumference by 3.14 to calculate the outside diameter of the well casing. Subtract 1/2″ to get your inner diameter. Length of string in inches / 3.14 = outside diameter of the well casing.