manner, the head loss is determined
for the 2-, 3-, and 6-inch diameter
allowable headloss Hf in the lines Al
and A2 to provide at least 20 psi at
(1) Main AB.
the latrine service connection and at
length = 1,400 feet.
least 30 psi at the laundry service
In paragraph 16b the
Allowable Hf = E1Tk - (E1Sc + Hreq)
where the required head is equal to
the required pressure in psi times
headloss to each building is then
calculated as follows:
Hf Al = 200-[140' + (2.31 x 20 psi)] =
Hf A2= 200[110'+ (2.31 x 30 psi)] =
The allowable headloss is determined
for the service connection only, and
not points on the main.
22. SAMPLE PROBLEM
The 2- and 3-inch pipes can be
eliminated at this point, as the
Select the pipe
exceed the maximum allowable from
point A to any point in the system.
headloss for the system.
The 4-inch pipe can be eliminated as
C = 100, and that pipe is available in
the headloss from A to B is greater
2-, 3-, 4-, 6-, 8-, 10-, and 12-inch
than the maximum allowed from A to
section of main from A to B will be
headloss to point B is now known for
The flow is 100 gpm; the
the size of pipe under consideration.
length 1,400 feet. From paragraph 17,
The pipe size for the branch line B1
the pipe size for the mains must be
can now be found. The total allowable
Two, three, four, and six-
headloss from point A to building 1 was
inch pipe will be tried.
computed as 13.8 feet.
14, 100 gpm in the left column is
headloss from A to B was found to be
connected to 4 inches in the second
2.4 feet if 6-inch pipe is used. This
The line is extended to
leaves 13.8 - 2.4 = 11.4 feet as the
intersect the third column as shown on
maximum that can be lost from point B
From the intersection of
to building No. 1 if 6-inch pipe is
used on the main AB. The length of the
headloss per 1,000 feet of pipe is
branch B1 is 400 feet. If 11.4 feet is
read as 12.5 feet.
Since the length
the largest allowable loss for 400