Water and wastewater · Worked step by step
How many feet of head is 50 psi?
If math has never been your thing, you are in the right place. Try it on paper first, then we write it out with you, one small step at a time, and explain every step in plain words so you never lose the thread.
The problem
A gauge reads 50 psi. How many feet of head does that pressure represent?
Grab a pen and paper first
Give it a real try on paper before you watch. If you get stuck, take a hint. If you go blank, that is fine, press play and we will walk it through together.
Watch it solved, with you
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Press play and I’ll write it out with you, one small step at a time.
Every step gets a plain-words explanation here, so you always know exactly what just happened and why.
The written version, step by step
- 1
Write down what you know
pressure = 50 psi • 1 psi = 2.31 feet of head
- The gauge shows 50 psi.
- Each 1 psi is worth 2.31 feet of water height.
- We want the feet, so we will use the 2.31.
Quick trick: 2.31 is on your formula sheet. It is the partner of 0.433 and goes the opposite direction.
- 2
Multiply psi by 2.31
feet = 50 × 2.31 • feet = 115.5
- 50 psi, each worth 2.31 feet, means 50 × 2.31.
- 50 × 2 = 100, and 50 × 0.31 = 15.5.
- Add them: 100 + 15.5 = 115.5 feet of head.
Quick trick: Feet came out bigger than psi (115.5 vs 50). That is the sign you multiplied the right way.
Remember this for good
To change psi into feet of head, multiply by 2.31. (Going the other way, feet to psi, you multiply by 0.433.)
Two partner numbers: 0.433 turns feet into psi, and 2.31 turns psi into feet. They are opposites. Feet make a smaller psi; psi makes a bigger feet number.
Solve it fast next time
- Psi given, feet wanted? Multiply by 2.31.
- Feet given, psi wanted? Multiply by 0.433.
- Check direction: feet should be a BIGGER number than psi, since 2.31 is more than 1.
The answer: About 115.5 feet.