Distribution Reservoir and Operating Storage
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Distribution Reservoir and Operating Storage

The water available from treatment plan is at a constant rate where as there is change in consumption rate so this needs to be balanced.

Therefore there are balancing reservoirs and distribution reservoirs care has to be taken to keep reserves for fire demand . The operating storage can be determined from mass diagram or hydrograph ( time discharge graph).

Tree system is also known as dead end system and grid iron system is known as loop system.

In grid iron system water can reach from alternate route but in case of tree system there is dead end. In case of repairs large area has to be cut off in tree system.

Determination of pipe diameter is done by starting with one assumption and calculating the head at the end , and if not sufficient then higher dia. Pipe is taken.

Alternatively nomograph can be used for design of pipe diameter.

The pipe lines are interconnected at 400 mts. Distance.

Fire hydrants should not be more than 170 meters apart and ideally located at cross junctions.

Using Hazen williams formula or other methods to compute the pressure at key points.

V=1.318C,R0.63, S0.54
V=Velocity in ft/sec, S=scope and R=hydraulic radius defined as below. R= A/P ( A is cross section of pipe and P wetted perimeter incase pipe is full then P is inside perimeter of pipe.

S=h1/I, h1 is loss due to friction and I is length of pipe.

Q= AxV= 0.281CxD2.63 x S0.54 Q= discharge, C is constant depending on material of pipe.

Value of C for different mat., Asbestos= 140, cast iron pipe=90 to 120 depending on age, concrete 120-140,copper130-140, plastic 140-150.
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