Ductile iron pipe is especially suited for pressure sewer applications because its standard wall thicknesses provide for high operating pressures with a minimum 20% surge allowance. Surges, or hydraulic transients, are a very serious problem for pressure sewers, as pump stations are vulnerable to power outages and surge control devices for raw wastewater are not always dependable. The surge forces, which can rupture some piping materials, are caused by momentum in the liquid due to change in velocity. Pressure sewers are designed much the same as water transmission lines. The Hazen-Williams formula is the most popular flow formula. The Hazen-Williams friction coefficient, "C," is generally accepted as 140 for cement-mortar linings and 150 for polyethylene and epoxy linings. Special linings are not usually specified if the pipe is always flowing full and the waste stream is domestic sewage. However, the designer has the option of the factory-applied linings to resist H2S as discussed under Gravity Sewers. In either case, the hydraulic efficiency of ductile iron pipe, coupled with its larger-than-nominal inside diameter, results in reduced pumping costs over the life of the pipeline. Piping for pressure sewers can be provided not only with push-on joints, but also with restrained joints having deflection capabilities after installation. All ductile iron force main piping can be interfaced with pumps, lift stations, and plant piping with standard fittings and factory-supplied spools.

Ductile iron pipe is often used for inverted siphons in difficult installations, such as the stream crossing shown here, because of its great strength, joint integrity, and its versatile and readily available joints and fittings.