To convert feet to PSI, what is the conversion factor?

To convert feet to PSI, what is the conversion factor?

• A. .433
• B. 2.31
• C. 1.0
• D. 0.5

Answer: (A)

In irrigation head pressure, you convert feet of water to pounds per square inch by using how much pressure a column of water exerts over an area. Water weighs about 62.4 pounds-force per cubic foot. A column 1 foot high on 1 square foot of area carries 62.4 pounds-force per square foot, which is 62.4/144 psi ≈ 0.433 psi. So each additional foot of head adds about 0.433 psi. This makes the conversion factor from feet to psi approximately 0.433. The inverse, 2.31, is the feet of head per psi, not psi per foot. Therefore the correct factor is 0.433.

In irrigation head pressure, you convert feet of water to pounds per square inch by using how much pressure a column of water exerts over an area. Water weighs about 62.4 pounds-force per cubic foot. A column 1 foot high on 1 square foot of area carries 62.4 pounds-force per square foot, which is 62.4/144 psi ≈ 0.433 psi. So each additional foot of head adds about 0.433 psi. This makes the conversion factor from feet to psi approximately 0.433. The inverse, 2.31, is the feet of head per psi, not psi per foot. Therefore the correct factor is 0.433.