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Maximum Depths of Cover

for Minimum Pressure Classes of Ductile Iron Pipe ANSI/AWWA C151/A21.51

This table tabulates the maximum depth of cover for the five types of laying conditions, along with corresponding nominal wall thickness and maximum rated working pressure, all for minimum pressure classes of ductile iron pipe. Taken from the table that follows, it is offered as a convenience for quickly checking the capabilities of minimum pressure classes of ductile iron pipe under a given set of conditions.

For the majority of internal pressure and external loading conditions, minimum pressure classes are more than adequate and possess substantial safety factors.

Size
(in.)		 Pressure
Class		 Thickness
(in.)		 Laying Conditions
Maximum Depth of Cover in Feet 1
Type 1 Type 2 Type 3 Type 4 Type 5
4 350 0.25 53 61 69 85 100 4
6 350 0.25 26 31 37 47 65
8 350 0.25 16 20 25 34 50
10 350 0.26 11 2 15 19 28 45
12 350 0.28 10 2 15 19 28 44
14 250 0.28 see 3 11 2 15 23 36
16 250 0.3 see 3 11 2 15 24 34
18 250 0.31 see 3 10 2 14 22 31
20 250 0.33 see 3 10 14 22 30
24 200 0.33 see 3 8 2 12 17 25
30 150 0.34 see 3 - 9 14 22
36 150 0.38 see 3 - 9 14 21
42 150 0.41 see 3 - 9 13 20
48 150 0.46 see 3 - 9 13 20
54 150 0.51 see 3 - 9 13 20
60 150 0.54 see 3 5 2 9 13 20
64 150 0.56 see 3 5 2 9 13 20

1 An allowance for single H-20 truck with 1.5 impact factor is included for all sizes and all depths of cover.

2 Minimum allowable depth of cover is 3’. For depths less than 3’, consult AMERICAN.

3 Laying condition Type 1 is limited to 12" and smaller pipe. For 14" and larger pipe, laying condition Type 1 should not be used.

4 Calculated maximum depth of cover exceeds 100’.

Maximum Depths of Cover for All Pressure Classes

Ductile Iron Pipe ANSI/AWWA C151/A21.51

This table lists maximum depths of cover for the five types of laying conditions for all standard pressure classes; also tabulated are the corresponding nominal wall thickness and maximum rated working pressure. (Note: Although not listed in the following table, ductile iron pipe for working pressures higher than 350 psi is available. Consult AMERICAN regarding specific conditions involved.)

Size
(in.)		 Pressure
Class
psi1 		Nominal
Thickness
(in.)		 Laying Conditions
Maximum Depth of Cover in Feet2
Type 1 Type 2 Type 3 Type 4 Type 5
4 350 0.25 53 61 69 85 1004
6 350 0.25 23 31 37 47 65
8 350 0.25 16 20 25 34 50
10 350 0.26 113 15 19 28 45
12 350 0.28 103 15 19 28 44
14 250 0.28 see5 113 15 23 36
14 300 0.3 see5 13 17 26 42
14 350 0.31 see5 14 19 27 44
16 250 0.31 see5 113 15 24 34
16 300 0.32 see5 13 17 26 39
16 350 0.34 see5 15 20 28 44
18 250 0.31 see5 103 14 22 31
18 300 0.34 see5 13 17 26 36
18 350 0.36 see5 15 19 28 41
20 250 0.33 see5 10 14 22 30
20 300 0.36 see5 13 17 26 35
20 350 0.38 see5 15 19 28 38
24 200 0.33 see5 83 12 17 25
24 250 0.37 see5 11 15 20 29
24 300 0.4 see5 13 17 24 32
24 350 0.43 see5 15 19 28 37
30 150 0.34 see5 - 9 14 22
30 200 0.38 see5 84 12 16 24
30 250 0.42 see5 11 15 19 27
30 300 0.45 see5 12 16 21 29
30 350 0.49 see5 15 19 25 33
36 150 0.38 see5 - 9 14 21
36 200 0.42 see5 84 12 15 23
36 250 0.47 see5 10 14 18 25
36 300 0.51 see5 12 16 20 28
36 350 0.56 see5 15 19 24 32
42 150 0.41 see5 - 9 13 20
42 200 0.47 see5 8 12 15 22
42 250 0.52 see5 10 14 17 25
42 300 0.57 see5 12 16 20 27
42 350 0.63 see5 15 19 23 32
48 150 0.46 see5 - 9 13 20
48 200 0.52 see5 8 11 15 22
48 250 0.58 see5 10 13 17 24
48 300 0.64 see5 12 15 19 27
48 350 0.7 see5 15 18 22 30
54 150 0.51 see5 - 9 13 20
54 200 0.58 see5 8 11 14 22
54 250 0.65 see5 10 13 16 24
54 300 0.72 see5 13 15 19 27
54 350 0.79 see5 15 18 22 30
60 150 0.54 see5 53 9 13 20
60 200 0.61 see5 8 11 14 22
60 250 0.68 see5 10 13 16 24
60 300 0.76 see5 13 15 19 26
60 350 0.83 see5 15 18 22 30
64 150 0.56 see5 23 9 13 20
64 200 0.64 see5 8 11 14 21
64 250 0.72 see5 10 13 16 24
64 300 0.8 see5 12 15 19 26
64 350 0.87 see5 15 17 21 29

1 These pipes are adequate for the rated working pressure indicated for each nominal size plus a surge allowance of 100 psi. Calculations are based on a 2.0 safety factor times the sum of working pressure and 100 psi surge allowance. Ductile iron pipe for working pressures higher than 350 psi is available.

2 An allowance for a single H-20 truck with 1.5 impact factor is included for all sizes and all depths of cover.

3 Minimum allowable depth of cover is 3’. For depths less than 3’, consult AMERICAN.

4 Calculated maximum depth of cover exceeds 100’.

5 Laying condition Type 1 is limited to 12" and smaller pipe. For 14" and larger pipe, laying condition Type 1 should not be used.

For other conditions not covered in these tables see AWWA C150 or consult AMERICAN for design of pipe thickness. Special thickness classes may be appropriate in such cases.

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