Abstract Twenty-seven well screens of various types and diameters were hydraulically tested in a specially designed and constructed test rig. A relatively simple model for describing the head losses was found to adequately summarize the observations, and this yielded two empirical parameters for each well screen. A comparison of screens of the same nominal diameter revealed only small differences. Although stainless-steel screens are much rougher than glass reinforced plastic (GRP) and plastic screens, their similar hydraulic behaviour is explained by the fact that they have significantly larger internal diameters (for the same nominal diameter). Screens of different diameters differ greatly: considerable reductions in head loss can be achieved by increasing the screen diameters.