main is filled slowly with water. Continue feeding
until the water discharged at the other end of the
section contains the desired residual chlorine. Let the
chlorinated water remain in the contaminated unit or
section for 24 to 48 hours. Then flush until the chlorine
residual is only that amount normally in the supply.
Make daily bacteriological analyses of water samples
until the analyses show no further disinfection is
When a chlorinator is not available, feed a strong
hypochlorite solution into the main from a pail through
the highest hydrant top or valve with the bonnet
removed. Add the hypochlorite and water until the
main is full and the chlorine residual is about 50 ppm.
Test the residual at the far end of the main. Bleed out
air trapped in the line.
When the mains are to be disinfected under
pressure by using supply or booster pumps, feed the
chlorine into the main with chlorinators or
hypochlorite feeders. Take care to ensure adequate and
accurate distribution of the disinfecting agent when
pumps are being used.
The use of dry calcium hypochlorite directly in
mains is not uniformly effective because of unequal
mixing with the water; therefore, when calcium
hypochlorite is used, prepare a solution of this
Natural contamination of water supplies can
increase because of emergencies. Standby or portable
chlorinators must be working to meet emergency
disinfection requirements in water-supply
components. This equipment should not be used to
make drinking water safe after bombing, sabotage, or
biological warfare has made water sources untreatable
with chlorine for disinfection.
Where pipes are exposed aboveground and in the
interior of buildings supplying air, water, or steam,
they must be supported adequately to prevent sagging.
This is because the weight of the pipes, plus the fluid in
them, can cause breaks, strain joints, and cause leaks in
The main supply pipe (vertical or horizontal) must
adequately supported to take its weight off the
ing and to prevent future leaks. Refer to figure 4-22
some methods of supporting cast-iron soil pipe and
Figure 4-22.Methods of supporting pipes.
galvanized pipe. Fixture supply risers are pipes
taken off of the supply pipes to furnish air, water, or
steam to the fixtures being installed. These risers
may be in the wall or exposed. They must be made
tight and tested before being closed up in a wall. All
vertical fixture risers should be supported at each
floor level or in a change of direction. They should
never be supported by the horizontal fixture supply