Question 1

Why is 1 psi = 2.31 ft?

Accepted Answer

1 psi is 1 lb of force on 1 in². Water weighs 62.4 lb/ft³ = 0.0361 lb/in² per inch of height. 1/0.0361 = 27.7 in = 2.31 ft.

Question 2

Does temperature matter?

Accepted Answer

Slightly. Hot water (200 °F) is ~96% the density of 60 °F water, so 1 psi = 2.41 ft. Usually negligible in water systems.

Question 3

What is the minimum distribution pressure?

Accepted Answer

Most states require ≥20 psi at all customer service connections under all flow conditions, per Ten States Standards.

Question 4

What's the maximum?

Accepted Answer

AWWA recommends ≤80 psi at customer service to limit leaks and fixture damage. Above 80 psi requires customer-side pressure-reducing valves.

psi ↔ Feet of Head Converter