Disinfection of Pipelines - Disinfection of Pipelines and Storage Facilities Field Guide - page 18

water changes within a pipeline. This volume is also the amount
that will need to be dechlorinated, if that is required. A useful field
estimate is to flush for about 2 minutes for each 100 ft of pipeline if
your flow rate is achieving a 2.5 ft/sec velocity.
The flow may be measured by a flowmeter or estimated using
the trajectory discharge method. Use Figure 3-3 to estimate the flow
using this method. Table 3-3 provides some calculated values using

Approximate flush volume for three water changes * Table 3-2

Volume in
100 ft of pipe

Volume for Three Water
Changes in 100 ft of pipe Pipe Diameter

in . mm gal L gal L

2 50 11, 16 11, 62 11,49 ,185

4 100 11, 65 1, 247 1,196 ,740

6 150 1, 148 1, 555 1,440 1,660

8 200 1, 261 1, 988 1,780 2,960

10 250 1, 408 1,540 1,220 4,630

12 300 1, 587 2,220 1,760 6,660

16 400 1,040 3,950 3,130 11,850

18 450 1,320 5,000 3,960 15,000

20 500 1,630 6,170 4,890 18,520

24 600 2,350 8,800 7,040 26,660

* Time to flush three water changes of 100 ft (30.48 m) at 1 ft/sec is about 5 min and
2 min at 2.5 ft/sec. The values in this table are calculated for US units and then
converted to SI units. Approximate volumes are acceptable for field applications.

Table
Tamer

This information is used to calculate the volume of water
within a pipeline and the amount needed for three water
changes. Example: 500 ft of 6-in. (152-mm) pipe needs
440 gal for 100 ft (from the table), so for 500 ft, 2,200
gallons are needed.

Ops Tip For each 100 ft (30.5 m) of pipe length flush for about 2 min.