The issue of changing the hydraulic characteristics of the pipelines previous being in operation is of great practical importance. To determine convenient objective parameters for assessing the reduction in pipeline throughput during their operation the experimental studies results of three sections of the pressure pipeline with artificial clogging were presented. It is shown that for pipelines with the same initial resistance at the same degree of clogging, the numerical values of the resistance coefficients are practically independent of the ratio of length to diameter. The rationale for the transition from traditional hydraulic resistance coefficients to filtration coefficients was given. The dependence of the relative filtration coefficient on the clogging degree is recommended as a universal characteristic of the throughput of pressure pipelines previous being in operation. It is proved that with small degrees of clogging, a relative decrease in the pipeline throughput occurs more intensively than with large degrees of clogging.