Planning to convert or drill wells for water injection or effluent disposal? You might want to consider an injectivity #welltest before designing surface equipment. I usually recommend a 24 h constant rate test followed by a 96 h pressure fall-off test. For pressure transient analysis (#PTA) a steady rate (i.e. time) is more important than maximum volume. Subsurface pressure recorders have multiple benefits: they satisfy #AER Initial Pressure requirements, the test isn’t over if the well goes on vacuum, and we don’t have to calculate sandface pressures with unknown friction or turbulence effects. Added values are reservoir engineering parameters: skin (s), permeability (k), reservoir pressure (p*), and a forecast stable injection rate for facility design and economics.