 First, every time water was admitted to the working vessel much of the heat was wasted in warming up the water that was being pumped.Secondly, the second stage of the process required high-pressure steam to force the water up, and the engine's soldered joints were barely capable of withstanding high pressure steam and needed frequent repair.Thirdly, although this engine used positive steam pressure to push water up out of the engine (with no theoretical limit to the height to which water could be lifted by a single high-pressure engine) practical and safety considerations meant that in practice, to clear water from a deep mine would have needed a series of moderate-pressure engines all the way from the bottom level to the surface.