Effective pipe fishways will significantly reduce the cost of restoring disrupted upstream fish passage. Various designs have been proposed over the decades, and three principal approaches have emerged: siphon fishways, the Fishheart system and the Tube Fishway. Their differing hydraulic behaviours will affect fish passing through them in different ways. This contribution reviews these approaches to highlight important design aspects that are likely to influence fish responses. Conventional hydraulic analysis has been coupled with novel numerical techniques to highlight the principal differences between approaches, illustrating performance at barriers 1, 10 and 50m height. Constraints on the performance of siphon fishways are exposed by the present analysis for the first time. The Fishheart system is reviewed in detail, with the analysis showing the hydraulic complexity associated with its valve operation systems. The Tube Fishway's unsteady operation is compared to these other systems in terms of observed fish behaviour and potential transport rates among upstream-migrating fish communities. Using pipe fishways at high (>10m) barriers becomes more challenging and the specific constraints are identified. Despite these constraints, pipe fishways hold the prospect of providing fish passage over high barriers and restoring fragmented river systems at scales that were not economically possible previously.