In this picture the water pressure in the water tank at the top of the water surface level is 0 feet of head, or you could also say there is 0 PSI. This is because the is no water above it to create pressure. Head is another word that indicates pressure, it is mostly used when measuring pressure created by the depth of water. So 10 feet of depth = 10 feet of head.
A few days ago I found Dultmeier saying you can multiply feet of head by .43 to get PSI. Rainbarrel Man says the same, but is easier to understand. (Dultmeier is more technical.) Also, Rain man uses .433, to get a little more accuracy in the PSI number.
2 comments:
Hey, this is from HomeTips.com, their Pipes & Home Plumbing for DIY Plumbers page:
"Remember that water pressure decreases by a half-pound per square inch for every foot pipes extend above your water supply."
I'm thinkin they said "half a pound per square inch" because they wanted to use a round number rather than 0.433 which is not a number designed for doing quick calculations in your head.
So what we have is that water pressure DECREASES when you go UP, and INCREASES when you go DOWN, in both cases by about half a PSI per foot of change in elevation. That makes sense.
Here's the same quote, in context. They're talking about the size of the water lines:
"In most cases, the main pipeline from the street to your home is either 3/4 or 1 inch in diameter, supply branches use 3/4-inch-diameter pipe, and pipes for individual components are 1/2 inch.
Remember that water pressure decreases by a half-pound per square inch for every foot pipes extend above your water supply. For ideal water pressure to second- and third-story fixtures, you might need a larger pipe."
if we multiply feet of head to get psi,
then we would divide psi by .433 to get feet of head.
so
if i want to achieve 60 psi
i would need 138 or 139 feet of head.
i guess that's why water towers are so high.
if i have a column of water four feet high,
at the bottom of it the psi is 1.73.
that's not very much.
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