Water pressure
Lift
Friction
Water pressure - Lift
To supply proper flow rate to upper stories, water must be lifted which requires pressure.
psi = pounds per square inch
static head = inches or feet of water that can be supported by a given pressure
one psi can lift a column of water 2.3 feet high, e.g., 10 psi can lift water 23 feet
additional pressure is needed to operate the fixtures at the highest level.
Calc example:
8 story building
14 foot floor to floor height
toilet requires 15 psi to flush
total lift = 8 stories X 14 feet per story = 112 feet
if 2.3 feet is equivalent to 1 psi, 112 feet is equivalent to 112/2.3 = 48.7 psi
Required water pressure
= 48.7 psi for lift + 15 psi for flush
= 63.7 psi
If water pressure from street is less than total required then other mechanical methods must be used to acheive proper pressure( this will be addressed shortly)
Converting
1 psi = 2.3 lift feet
then
.433 psi = 1 lift feet
faucet =
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