The CVS Controls gas driven Series 51 Injector uses a molded diaphragm to drive a piston through the chevron packing making it a positive displacement pump, capable of discharge pressures up to 6000 PSIG. A pilot valve directs incoming operating gas behind the diaphragm, which causes the diaphragm to stroke forward. The valve shuts off the inlet pressure and opens to expel the spent gas behind the diaphragm and the cycle repeats. A choice of three plunger sizes, and two stroke lengths, allows for a wide range in capacity, from less than one quart to 30 gallons per day.