A reverse flow diverter (RFD) is a key fluidic component in RFD pumps, which are air‐powered, low‐maintenance devices used for transferring hazardous liquids. Despite several decades of practical application, no clear characteristic numbers exist for the suction ratio q = 1.0 and for the peak value of q, nor are there clear dimensionless performance curves for the reverse‐flow portion of the pumping cycle. We experimentally investigated the effects of suction gap length and nozzle exit diameter on RFD flow and pressure under the condition of diffuser entrance to nozzle exit area ratio of m = 1.0. The results were used to derive two dimensionless performance curves (q = A · exp[−δ/B] + C · exp[−δ/D] + E and q = k · α + F) and characteristic numbers at q = 1.0 and the peak value of q. These curves and numbers are useful to simplify the design program and ease the selection of operation parameters for RFD pumping systems. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.