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Water Management. Water is an important natural resource that requires proper management. Appropriate flow rate, pressure, and water quality are necessary for effective use. Water System. WATER SUPPLY. TREATMENT. STORAGE. DISTRIBUTION. CONSUMER. Supply. Treatment. Storage. 35-50 psi. - PowerPoint PPT Presentation
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Water Management
Water is an important natural resource that requires proper management.
Appropriate flow rate, pressure, and water quality are necessary for effective use.
Water System
WATER SUPPLY
STORAGE
TREATMENT
CONSUMER
DISTRIBUTION
Supply
Treatment
Storage
Consumer
1 psi = 2.31 ft of water
35-50 psi
Terminology
Static pressure (head):No water flowing through the system
Head loss:Pressure loss due to friction
Actual pressure:Static pressure – head loss (all expressed in
psi)
Hazen-Williams Formula
hf = 10.44 * L * Q1.85
C1.85 * d4.8655
Where: hf = head loss due to friction (ft) L = length of pipe (ft) Q = flow rate of water through
the pipe (gpm) C = Hazen-Williams constant d = diameter of the pipe (in.)
Water Supply ProblemA business’s water supply connection at the street is at elevation 1,257 ft and has a pressure of 55 psi. The first floor fixture elevation is 1,285 ft. Between the connection and a first floor fixture, there are 120 ft of 3 in. copper pipe, 25 ft of ¾ in. copper pipe, and five (5) ¾ in. - 90o elbows. Discharge through the fixture is 10 gpm. The equivalent length for a single ¾ in., 90o elbow is 4 ft. The Hazen-Williams constant for copper pipe is 140.
Water Supply Problem
What is the pressure loss due to elevation change between the street connection and the first floor fixture?
1st floor elevation – street elevation
1,285 ft – 1,257 ft = 28 ft
Convert to psi:
28 ft ÷ 2.31 ft/psi = 12.12 psi
Total Equivalent Length of ¾ in. Pipe
= Pipe length + fitting equivalent length
= 25 ft + (5 elbows * 4 ft/elbow)
= 45.00 ft
Head Loss in ¾ in. Pipe
Friction head loss using Hazen Williams equation
hf = 10.44 * L * Q1.85
C1.85 * d4.8655
hf = 10.44 * 45 ft * (10 gpm)1.85
(140)1.85 * (3/4 in.)4.8655
hf = 14.44 ft
Head Loss in 3 in. Pipe
hf = 10.44 * L * Q1.85
C1.85 * d4.8655
hf = 10.44 * 120 ft * (10 gpm) 1.85
(140)1.85 * (3 in.) 4.8655
hf = 0.05 ft
Total Head Loss for ¾ in. & 3 in. Pipe
Total Head Loss (due to friction):
= Head loss, ¾ in. pipe + head loss, 3 in. pipe
= 14.44 ft + 0.05 ft
= 14.49 ft
Convert to psi:
14.49 ft ÷ 2.31 ft/psi = 6.27 psi
Water Supply Problem
What is the pressure in units of psi at the first floor fixture?
Actual pressure = street pressure – static difference – head loss
= 55 psi – 12.12 psi – 6.27 psi = 36.61 psi