Roughness Coefficient - CivilWeb Spreadsheets

Equivalent Sand Roughness Coefficient (ks) (m)

The Roughness Coefficient is a measurement of the average roughness of the wetted perimeter of a pipe or conveyance. This allows the Colebrook-White formula to correct for the effect of this roughness slowing down the water as it moves through the pipe or conveyance. Typical values are given below;

Equivalent Sand Roughness (ks)
Surface Water	Suggested Design Value	Likely Range
Asbestos Cement	0.03		0.015	0.03
Precast concrete pipes with 'O' ring joints	0.15		0.06	0.6
Clayware	0.06		0.03	0.15
Pitch Fibre	0.03
Glass Fibre	0.06
UPVC
With chemically cemented joints	0.03
With spigot and socket joints, 'O' ring seals at 6 m to 9 m intervals	0.06
Brickwork
Glazed	1.5
Well pointed	3
Old brickwork	15

Combined Sewers	Good		Normal	Poor
Concrete	0.6		1.5	3
Asbestos Cement	0.6		1.5	3
Clayware	0.6		1.5	3
UPVC	0.3		0.6	1.5

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