Abstract: A single acting dual piston positive displacement pump with alternating piston motion. A pump suitable for manual operation and operable at relatively high pressure such as 400 to 800 psig. A pump suitable for pumping corrosive liquids with the drive mechanism separated from the liquid lines. A pump housing with cylinder section and abutting manifold section, with the alternating reciprocating pistons in the cylinder section and the inlet and outlet openings in the manifold section, with the pistons projecting from the cylinder section opposite the inlet and outlet openings for connection to the piston drive mechanism.