Storm Water Drainage System Calc

8/3/2019 Storm Water Drainage System Calc

1/11

PIPE GRADE REGULATION

Pipe grade is dependant on the level of the pipe outlet to achieve drainage, the grade of the surface, avoiding obstacles and other pipes,

and cover requirements. For a first trial use the grade of the surface

If the surface is flat, the code requires the use of the minimum allowable grades as shown below :-

PIPE SIZE PIPE SIZE

90 1:100 1:90 225 1: 200 1: 350

100 1:100 1:120 300 1: 250 1: 350150 1:100 1: 200 375 1: 300 1: 350

Note, for Australia a 150 dia pipe requires a grade of 1:100, the same grade as required for a 100 and a 90 dia pipe.

I believe this to be a misprint and should be 1:150, as larger pipes generally require a flatter grade.

By the way, the purpose of a minimum grade is hopefully to ensure a self cleansing velocity during periods of low flow.

Also, the Code only refers to the "Nominal Diameter". The actual Internal diameter may be slightly more or less, depending on the material c

MIN GRADEAUST

MINGRADE NZ

MINGRADEAUST

MINGRADE NZ


2/11


3/11

CONT.No.:

DATE :

BY :

CHECKED :

DATE :

FLOW IN PIPE - MANNING FORMULA SHEET No:

Project:

Subject:

Data :

Roof Area ( 60m x 34 m) = 2040 M2

CASE I

Rainfall Intensity = 30 mm/h 0.03 m/h

Q (m3/h) = 61.2

Q (m3/s) = 0.02

Drain pipe run out = 2 Nos

Pipe dia Selection = 200mm

Flow required Q (d) = 0.008 m3/s

Coefficient of surface roughness n = 0.009

Slope of Pipe S = 1 Vertically 200 Horizontal. 0.5

Grade Selected = 1 : 200 ( See Grade regulation Australia Std )

Diameter of Pipe D (mm) = 200 0.20 m

PIPE FULL

Manning Formula Q = 0.312/ n* (D)^8/3*S^1/2

Manning Formula V = 0.397/ n* (D)^2/3*S^1/2


4/11

CONT.No.:

DATE :

BY :

CHECKED :

DATE :


Project:

Subject:

CASE II

Rainfall Intensity = 50 mm/h 0.05 m/h

Q (m3/h) = 102

Q (m3/s) = 0.03

Drain pipe run out = 2 Nos

Pipe dia Selection = 200mm






PIPE FULL



Velocity V = 1.07 m/s (MIN 0.8 , MAX 3 M/S)

Discharge Q ( f ) = 0.0335 m3/s Qf>Qd


5/11

CONT.No.:

DATE :

BY :

CHECKED :

DATE :


Project:

Subject:

CASE III

Rainfall Intensity = 100mm/h 0.10 m/h

Q (m3/h) = 204

Q (m3/s) = 0.06

Drain pipe run out = 2 NosPipe dia Selection = 200mm






PIPE FULL



Velocity V = 1.07 m/s (MIN 0.8 , MAX 3 M/S)

Discharge Q ( f ) = 0.0335 m3/s Qf>Qd


6/11

CONT.No.:

DATE :

BY :

CHECKED :

DATE :


Project:

Subject:

STORM DRAIN PIPE/GUTTER PERFORMANCPipe/Gutter flow ability > Rain Flow ( Qf/Qd > 100 %)

CONDITION Wetted Radius/depth pipe

( RAIN WATER INENSITY) Full 75% 50%

Case I 30 mm/h OK OK OK Case II 50 mm/h OK OK OK

Case III 100 mm/h OK OK x

CONCLUSION

2 Nos Gutter/Pipe drain with dia 200 mm each


7/11

11-Feb-12

Herawan

1

%


8/11

11-Feb-12

Herawan

1

%


9/11

11-Feb-12

Herawan

1

%


10/11

11-Feb-12

Herawan

1

E


11/11

A. Volume of Rainfall for the Area of roof

(Precipitation)

CASE1 30mm/hour

Q=0.03m/h2,040m2=61m3/h

CASE2 50mm/hourQ=0.05m/h2,040m2=102m3/h

CASE3 100mm/hour

Q=0.10m/h2,040m2=204m3/h

B Gutter pipe flow ability (using D200 2pipes)

Water occupied area for pipe

CASE1 Pipe 50%

Q=(0.2^23.14/450%)1.07m/S3,600S2pipes=121m3/h

CASE2 Pipe 75%

Q=(0.2^23.14/475%)1.21m/S3,600S2pipes=205m3/h

CASE3 Pipe 100%

Precipitation per pour is generally 10~30mm/hour

It is rare rainfalling 100mm/hour

Q=(0.2^23.14/4100%)1.07m/S3,600S2pipes=242m3/hPrecipitation 100mm/h

Documents

Storm Water Drainage System Calc