High efficiency, high pressure pump suitable for remote installations and solar power sources

A pump head has a motor coupler; a motor mount; at least one piston housing; a fluid input; a fluid output; and a reciprocating piston to pump a fluid from fluid input to fluid output. The manifold has fluid input and output bores extending parallel with the reciprocating piston, and from end to end thereof. The motor mount has a mounting flange configured to couple to a motor, and a torsion sleeve extending from the flange. A torsion bolt is coupled with the piston housing. An elastomeric sleeve isolates the torsion bolt from torsion sleeve. The torsion bolt longitudinally compresses and radially expands the elastomeric sleeve toward and against the torsion sleeve. The reciprocating piston, piston housing, a first seal, and a second seal in combination define a fluid collection chamber for fluid that leaks past the first seal. A fluid conduit connects the fluid collection chamber to the fluid input. An over-pressure release valve assembly is coupled on an input with the fluid output from the pump head, and is configured to stay closed until a predetermined maximum pressure is exceeded, and when opened will spill fluid back to at least one of the fluid inlet or a fluid reservoir.