SME
Hydraulics & Hydrology · Problem type
Head loss by Hazen–Williams
Use this for “0.1 m³/s of water runs through 500 m of 0.3 m pipe with C = 130. What is the head loss?”
Diagram
The
energy
grade
line
falls
by
hL
=
3.21
m
along
the
pipe;
the
hydraulic
grade
line
runs
V
2
2g
=
0.102
m
under
it.
Heads are to the scale at the left; the pipe’s length is not.
Roughness, Hazen–Williams C C = 130
This is an example. Type your own values to start a new problem.
hf (m)
=
10.67
×
L (m)
×
(
Q (m³/s)
)
1.852
C
1.852
×
(
D (m)
)
4.87
Formulas
hf
=
10.67
×
L
×
Q
1.852
C
1.852
×
D
4.87
3.2102
=
10.67
×
500
×
0.1
1.852
130
1.852
×
0.3
4.87
Assumptions
•
Water in turbulent flow at ordinary temperatures, the conditions the formula was fitted to.
•
SI form: Q in m³/s, D and L in m; C is about 130 to 140 for new ductile iron or PVC.
•
Minor losses are ignored.
Step-by-step
WE KNOW
Q = 0.1 m³/s, D = 0.3 m, L = 500 m, C = 130
FIND
head loss (hf)
Step 1 · Find head loss (hf)
Use hf = 10.67 × L × Q1.852 ÷ (C1.852 × D4.87)
Longer,
fuller
and
narrower
pipes
lose
more
head;
a
smoother
pipe
(larger
C
)
loses
less.
hf
=
10.67
×
500
×
0.1
1.852
130
1.852
×
0.3
4.87
hf
=
10.67
×
500
×
0.01406
23.367
hf = 3.2102 m
Check
Put the numbers back in. Both sides should match.
3.2102
=
10.67
×
500
×
0.1
1.852
130
1.852
×
0.3
4.87
✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
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