How do I measure my well casing to determine what size of well cap I need?

Good news! Measuring the well casing to determine the required well cap size is quite simple.

Well caps are sized by the nominal well casing size which is controlled by the well casings inside diameter (ID) (up to 12”). For 14” and larger well casings the size is controlled by the outside diameter.

What you need to measure is the outside diameter of the casing. Well caps are designed to seal on the outside diameter (O.D.) of the well casing. This measurement can be easily obtained using a measuring tape.

STEP #1 - Hook the end of the tape measure on one side of the well casing.

STEP #2 - Pull the tape measure back across the center point of the well casing to the opposite side. Move the tape side to side until you find the largest dimension (this ensures you are measuring at 180° across the casing).

STEP #3 - Take note of the measurement to the nearest 1/16th inch. This measurement will correspond with the well cap size as per the chart below.

CAUTION: Do not confuse a well cap for a well seal.

Unlike well caps, the well seals are designed to seal on the inside diameter of the well casing.