Compared to cast iron, clay and vitreouspipe systems, stainless steel pipes havea considerably smoother bore (ManningCoefficient: 0.011) and in general, areless susceptible to internal scaling.
In some instances, low roughness coefficients (ks) are not generally a true reflection of the long-term hydraulic performance of the installed system.Roughness coefficients of 0.6mm should be used for rainwater/storm drainage and 1.5mm for soil/foul drainage.
Two sets of flow tables are presentedwithin this design guide.
Table 1 is for pipes installed with level (or nearly level) gradients where the steady,uniform flow equations are not applicable.The data therefore has been generated from ACO's hydraulic design program'Hydro' that is based on the equations of spatially-varied flow.
Table 2 is for pipes installed with varying gradients. The data is based on the Colebrook-White equation using an appropriate roughness coefficient for stainless steel.
When draining storm or foul water, it is inevitable that sediment deposits will occur within the drainage system.
Sediment and scale deposits will reduce the flow rate through any pipe system and it is recommended that an allowance is made for this within the design and planning phase.