Primers are an important piece of the solvent cement process and are required by building codes for most applications. They help to prepare the pipe and fitting for solvent cementing by cleaning and softening the pipe and fitting making sure that the final joint integrity is maximized. For most cases, a cleaner should be used, followed by a primer and then the solvent cement. Additionally, after application of the primer, the solvent cement should be applied immediately before the primer dries. Note that primers should NOT be used for ABS pipe and that cleaner should be used in its place.