Plateau Pipe Company
Manufacturer of corrugated metal pipe

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 Multiple Culvert Installation
 This table shows the number of smaller diameter culverts equal in the water carrying capacity to that of one  culvert of larger size. It is based on culverts laid on the same slope.

 EXAMPLE:   One 24” diameter culvert is equivalent to five 12” culverts or two 18” culverts in water carrying  capacity.

Diameter in Inches 

 12" 15" 18" 21" 24" 30" 36" 42" 48" 54" 60" 66" 72" 84"

12”
15”
18”
21”
24”
30”
36”
42”
48”
54”

1
1
1
1
1
1
1
1
1
1

 1.7
1.5
1.4
1.4
1.7
1.5
1.4
1.4
1.3
1.3		 2.5
2.2
2
2.3
2.5
2.2
1.9
1.8
1.7
1.6
 3.6
3
3
3.5
3.6
3
2.6
2.3
2
1.9		 5
5
5
5
5
4
3.3
2.8
2.5
2.8		 8
8
7
7
6.5
5
4
3.5
3.6
 12
11
10
9
8
6
5
5

 18
15
13
11
10
7.5
7		 24
19
16
14
12
11		 32
25
20
17
18		 41
29
25
25





 51
37
35

63
53




 90



  FULL CIRCLE DRAINAGE TABLE
 This chart is based on Talbot’s formula for determining correct culvert sizes for the area to be drained.

Diameter in Inches 

 12" 15" 18" 24" 30" 36" 42" 48" 54" 60" 66" 72" 78" 84"

Area of Waterway Opening in 16.000 Sq. Ft.

0.785

1.227

1.767

3.142

4.909

7.068

9.621

12.566

38.484

19.635

23.760

28.274

33.183

 38.484
Acres of Mountainous Country

¾

1

2

5

8

14

20

29

40

55

70

  85

105

130
Acres of Rolling Country

3

6

9

20

36

59

89

125

175

230

295

375

460

560

Acres of
Level
Country

6

11

18

39

71

115

175

250

345

455

585

735

910

1110