in the present application to refer to seals which allow fluid passage easily in only one direction a simple example and the presently preferred embodiment is the vee lip seal however many other seal designs are possible as detailed in the seals and sealing handbook 4 ed m brown 1995 fig1 a 1c show a first sample embodiment in which a hydrostatically asymmetric seal 130 is integrated with the bladder concave diaphragm 100 a of the pressure compensator 100 fig1 a shows the bladder 100 a with a hydrostatically asymmetric seal 130 as its lip in place in the pressure compensator fig1 b shows how the hydrostatically asymmetric seal 130 of this embodiment allows free flow in one direction and fig1 c shows how this seal 130 blocks reverse flow note that in these embodiments the lubricant first passes into the concavity 102 and only from there escapes past the seal pressure relief valve to relieve overpressure fig1 d 1e show a second embodiment in which a hydrostatically asymmetric seal 130 d is still integrated with the bladder concave diaphragm 100 d of the pressure compensator but is turned in the opposite direction to the embodiment of fig1 a fig1 d provides an sectional view of the bladder 100 d with a hydrostatically asymmetric seal 130 d as its turned down lip in place in the pressure compensator and fig1 e shows.