Liquid Piston Pumps are considered to be systems involving the up and down oscillations of a fluid column contained in a vessel which is enclosed at the top. At the bottom a suitable arrangement of check valves converts the oscillatory motion to a pumping action. The oscillations may be generated by cyclic heating, inertia forces, or combinations of the two. Existing designs of LPP’s are reviewed. Experimental results, and a theoretical analysis, are given for a straight tube L.P.P. The design of a Solar LPP is presented, which appears to be a practical and simple means of converting heat energy from a solar panel to potential energy of a water reservoir.