Plumbing Systems 5-Storm Water Drainage System

7/27/2019 Plumbing Systems 5-Storm Water Drainage System

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PLUMBING SYSTEMS(STORM WATER DRAINAGE

SYSTEM)-5


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STORM WATER DRAINAGE SYSTEM

Rational formula for calculating runoff = Q = (C I A) / 360

Q = Runoff in m3/sec

I = Intensity of rainfall in mm/ hr.

A = Drainage area in hectares.

C = Co-efficient of run off as below

Run-off co-efficient for various types of surfaces

Open grounds, unpaved street 0.30

Parks, lawns, gardens 0.20 to 0.50

Macadam roads, pavements 0.70

Asphalt pavements 0.85 to 0.70

Water tight roof surface 0.95

The object of storm water drainage is to collect and carry, the

rain-water collected within the premises of the building, for

suitable disposal.


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Recommended Slopes for Roofs:- 1: 150 -1:200


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INDICATION OF TERRACE RAIN WATER


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RAIN WATER HARVESTING SYSTEM

Proposed to collect roof top rain water & reuse for various

purposes after necessary treatment.

Sub- surface recharge pits are proposed at strategiclocation to recharge the occupier, the same schemeshall be submitted to authorities for their approvalbefore implementing.


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PODIUM SUBSOIL DRAINAGE ARRANGEMENT


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Rational formula for calculating runoff = Q = (C I A) / 360

Run-off co-efficient for various types of surfaces0.3

Parks, lawns, gardens 0.20 to 0.50

0.7

Asphalt pavements 0.85 to 0.70

0.95

Total Run-off : ROOF TOP of Monday, Wednesday & Friday Blocks

113.313 m3/day

32.3 mm/day

3692.79 Sq.m

0.95

Considering 24Hr Rain fall with intensity of 32.3mm per day based on the metrological data

Volume of rainwater available for harvesting 113 cum

(after first flush of water about 10% )

This run-off is being diverted to roof top water collection sump,

which shall be used for domestic purposes after the necessary treatment

Total Run-off : ROOF TOP of Thursday Block

15.036 m3/day32.3 mm/day

490.00 Sq.m

0.95

Considering 24Hr Rain fall with intensity of 32.3mm per day based on the metrological data

Volume of rainwater available for harvesting 15 cum

(after first flush of water about 10% )

This run-off is being diverted to External drain

The drain rechage through Gravity head Recharge wells

Q = RunoffI = Intensity of rainfall

A = Drainage area in sq.m.

C = Co-efficient of run off

Data assumed:

A = Drainage area in sq.m.


Data assumed:

C = Co-efficient of run off as below

Open grounds, unpaved street

Macadam roads, pavements

Water tight roof surface

Q = Runoff

I = Intensity of rainfall

Q = Runoff in m3/sec

I = Intensity of rainfall in mm/ hr.


DESIGN DETAILS Total Run-off : POIUM HARDSCAPE & DRIVEWAY AREA

0.105 m3/sec

30 mm/hr

1.80 Ha

0.7

Volume of rainwater avai lable for harvesting is 60% 57 cum

Now it is considered that the

Total depth of chamber 3 m. BGL

Total depth of filter material in the chamber 1.5 m

Voids in the combination of filter material 40%

Depth of effective open space in the chamber 1.5 m

Soak Pit calculation

0.1 m/hr

2 mtr

3.142 Sqm

18.852 Sqm

21.994 Sqm

2.1994 Cum/hr

33 Nos.

71.74 Cum

0 Cum

Total area of per soak pit

Total water permeability/pit/hour

Total number of Percolation pits required

Amount of water perculating through the soak pits

Hence, provide soak pits in the area at approx 20 m c/c.

Excess water is find its way to external public drains in worst rainfall

Data assumed:

Infiltration rate is 10 cms/hr

Soak pit of 2 m diameter is considered

Area of bottom surface of soak pit

Area of wetted perimeter of Soak pit


Data assumed:

Considering 15 min of rainfall

(Losses due to runoff, evaporation and evap-transpiration is 40% )

Q = Runoff

I = Intensity of rainfall


CALCULATION FOR RAIN WATER HARVESTING


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Hydraulic Principle:

When a full bore flow is established in a vertical stack, the dropping

water accelerates due to the force of gravity and creates a syphonic action in the water

in the upper parts of the system. This literally gets sucked into the flow. The greater the

height difference in the stack, the higher the potential energy available, and the stronger

the suction effect.

Creating negative pressure in roof drainage piping improves the performance

of the system.

Working principle:

Ingenious gravity induced vacuum principle.

Pluvia System


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Pluvia System

Only water

Conventional System

Water

Air

Approximately 1/2 the diameter

of a conventional system

Pluvia System


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Pluvia In Various Stages During Rainfall

Pluvia system installed Low rainfall

More rain more water and less air

...designed for peak rainfall


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Pluvia System

One down pipe only

9 l/s 9 l/s 9 l/s

75 90110

200 27 l/s

A large number of down pipes

4.5 l/s 4.5 l/s 4.5 l/s

4.5 l/s 4.5 l/s 4.5 l/s

110 110 110

160 200

27 l/s

Conventional System


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Pluvia System

No slope required

Slope 1-3%

Conventional System


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Plumbing Systems 5-Storm Water Drainage System

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