Disinfection of Pipelines - Disinfection of Pipelines and Storage Facilities Field Guide - page 37

5. Contain the water in the pipe for at least 24 hr. Hold the
water for at least 48 hr if the water temperature is less
that 41°F (5°C). Optionally, water may be supplied from a
temporary connection with an appropriate backflow
prevention device. Bleeding a small amount of water from
the pipe occasionally during the holding period will
ensure that chlorinated water is well distributed
throughout the pipe.
6. A detectable chlorine residual must be present at each
sampling point (see section on bacteriological testing)
after the holding period.

Chlorine Amount Calculation
Use Tables 3-7a & b and 3-8a & b to determine the amount of
chlorine needed using the tablet method for pipeline disinfection.
This method requires that chlorine in the form of tablets or gran-
ules is placed in the pipe so that when filled with water the
chlorine dosage is at least 25 mg/L.
Use the chlorination chemical amount calculation checklist on
page 28.
❑

The pipeline diameter and length are used to calculate the
volume of the pipeline from Table 3-6.

❑ The number of valves, hydrants, and other appurtenances

determine the number of tablets needed for disinfection of
these items. Usually one tablet for each is adequate.

❑ This method requires that the entire pipeline is filled with

water so the volume of the pipeline is the same as the vol-
ume of chlorination water (Table 3-6)

The amount of chlorine chemical needed for the job comes
from Tables 3-7a, 3-7b, 3-8a, or 3-8b, depending on the
length and size of pipe and whether granules or tablets are
used. Table 3-7b shows the approximate number of kitchen
measures needed if there is no way to weigh the chemical
in the field.
Study the examples below to gain a more complete under-
standing of how to make this calculation.

❑