Enter the pipe diameter (in), the length of the pipe (ft), and the purge rate (cfh) into the Purge Time Calculator. The calculator will evaluate the Purge Time.

## Purge Time Formula

The following formula is used to calculate the Purge Time.

PT = pi*D/12*L/PR*60

Variables:

- PT is the Purge Time (minutes)
- D is the pipe diameter (in)
- L is the length of the pipe (ft)
- PR is the purge rate (cfh,ft^3/hr)

To calculate the purge time, multiply the diameter by pi, multiply again by the length, divide by the purge rate, then finally multiply by 5.

## How to Calculate Purge Time?

The following steps outline how to calculate the Purge Time.

- First, determine the pipe diameter (in).
- Next, determine the length of the pipe (ft).
- Next, determine the purge rate (cfh).
- Next, gather the formula from above = PT = pi*D/12*L/PR*60.
- Finally, calculate the Purge Time.
- 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.

pipe diameter (in) = 4

length of the pipe (ft) = 100

purge rate (cfh) = 2.5

PT = pi*D/12*L/PR*60 =** ** ?