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5.9 Appurtenances 185
concrete pipe are perhaps the most difficult, but they are rarely required. Cast-iron and
small welded-steel pipes can be cleaned by scraping machines and lined in place with ce-
ment to restore their capacity. New lines and repaired lines should be disinfected before
they are put into service.

5.8.7 Leakage
All pipelines should be tested for tightness as they are constructed. Observed leakage is
often expressed in gal/day/in. diameter (nominal)/mile of pipe using the U.S. custom-
ary units, or in L/day/mm diameter (nominal)/km of pipe using the SI units. The test
pressure must naturally be stated. To conduct a leakage test, the line is isolated by clos-
ing gates and placing a temporary header or plug at the end of the section to be tested.
The pipe is then filled with water and placed under pressure, the water needed to main-
tain the pressure being measured by an ordinary household meter. Where there is no
water, air may be substituted. Losses are assumed to vary with the square root of the
pressure, as in orifices.
The allowable leakage of bell-and-spigot cast-iron pipe that has been carefully laid
and well tested during construction is often set at

nd1p
Q = (U.S. Customary Units) (5.43a)
1,850

where Q is the leakage, gal/h; n is the number of joints in the length of line tested, d is the
nominal pipe diameter, in.; and p is the average pressure during test, psig. A mile (1.6 km)
of 24-in. (600-mm) cast-iron pipe laid in 12-ft (3.6-m) lengths and tested under a pressure
of 64 psig (444 kPa), for example, can be expected to show a leakage of:

Q = (5,280>12) * 24 * 164>1,850 = 46 gal/h (174 L/h)

Considering that the pipe has a carrying capacity of 250,000 gal/h (946,000 L/h) at a veloc-
ity of 3 ft/s (0.90 m/s), the expected leakage from joints (46 24 gal/day)/24 in./mile
46 gal/day/in./mile, which is relatively small.
The equivalent metric leakage equation using the SI units is as follows:

nd1p
Q = (SI Units) (5.43b)
32,500

where Q is the leakage, L/h; n is the number of joints in the length of line tested; d is the
nominal pipe diameter, mm; and p is the average pressure during test, kPa. For the same
example introduced above, the expected leakage calculated using SI units is

Q = 3(1.6 * 1,000>3.6) * 60014444>32,500 = 173 L/h
The expected leakage from joints is equal to (173 24 L/day)/600 mm/1.6 km
4.3 L/day/mm/km.

5.9 APPURTENANCES
To isolate and drain pipeline sections for test, inspection, cleaning, and repairs, a number
of appurtenances, or auxiliaries, are generally installed in the line (Figs. 5.12 and 5.13).