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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.
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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
35-50 psi Consumer 1 psi = 2.31 ft of water
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 Problem • A 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 4ft. 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