PACKAGE : I Bid Document VOLUME : II - Public Health Engineering

11.9 Flanged joints.
Flanged joint should be made by painting the facing of the flange with white lead
freely and bolting up evenly on all sides. A thin fibre of lead wool may be very
useful in making the joints water tight where facing of the pipes is not true.
When packing must be used, it should be of rubber insertion three ply and of
approved thickness. The packing should be of the full diameter of the flange with
proper pipe hold and bolt holes cut out evenly on both the inner and outer edges.
Where the flange is not full faced, the packing may be of diameter of the packing
strip only, proper placing of the packing should be checked before another pipe is
jointed on.
11.10 Disinfection of Mains.
Upon completion of a newly laid main or when repairs to existing pipes are made,
the main shall be disinfected as directed by the Engineer.
The main shall be flushed prior to disinfection except when the tablet method is
used. After initial flushing, the hypochlorite solution shall be applied to the water
main with mechanically or electrically powered chemical feed pump designed for
feeding chlorine solutions. For small applications, the solution may be fed with a
hand pump.
In the case of mains of large diameter, water from the existing distribution system
or other approved source shall be made to flow at a constant measured rate into the
newly laid pipeline. The water shall receive a dose of chlorine also fed at a constant
measured rate. The two rates shall be proportioned so that the concentration in the
water entering the pipeline is maintained at not less than 300 mg/l. The chlorine
shall be applied continuously and for a sufficient period to develop a solid column
of ‘Slug’ of chlorinated water that will, as it passes along the line, expose all
interior surfaces to a concentration of at least 300 mg/l for atleast 3 hours. As the
chlorinated water flows through tees and crosses, related valves and hydrants shall
be operated so as to disinfect the appurtenances.
In the case of newly laid mains in which scrupulous cleanliness has been exercised,
the tablet method can be adopted and in this method, the initial flushing is
dispensed with. The calcium hypo chlorate tablets, are placed in each section of
pipe and also in hydrants, hydrants branches and other appurtenances. The tablets
shall be attached by an adhesive and must be at the top of the main. The main shall
then be filled with water and the water shall remain in the pipe for atleast 24 hours.
GTS : General Technical specification. Page 91