Abstract: A diaphragm pump is powered by fluctuating pressure in a pressurized conduit. A three way valve is cycled to alternately pressurize and vent the pump. A power diaphragm drives a piston having a skirt with a reduced end wall to displace a quantity of hydraulic fluid from a pump chamber to drive a pumping diaphragm. An inlet of the pump admits a quantity of fluid to be discharged via a pump outlet. A spring component biases the piston to return same upon venting of the pressurized conduit. The diaphragm pump is shown in a pumping system wherein a primary pump and an intermittently cycled three way valve operate the diaphragm pump to inject fluid into the output conduit from the primary pump.