Pressure-driven metered mixing dispensing pumps and methods

A pressure-driven metered mixing dispensing pump, comprising:

• a housing;
• a piston disposed in the housing at least partially defining first, second and third chambers within the housing;
• the first and second chambers in fluid communication with the third chamber;
• and
• a first one-way valve positioned between the second chamber and the third chamber;
• wherein the piston is selectively controllable to move between a first position and a second position:
• wherein in the first position, substantially none of a first fluid in the first chamber is directed into the third chamber;
• wherein in the second position, a volume of the first chamber is expanded and substantially all of the first fluid in the first chamber is directed into the third chamber and a volume of the second chamber is contracted causing a second fluid from the second chamber to enter the third chamber and be mixed in the third chamber with the first fluid from the first chamber;
• and
• wherein the first fluid entering the first chamber causes the piston to move from the first position to the second position.

A pressure-driven metered mixing dispensing pump, comprising:

• a housing;
• a piston disposed in the housing at least partially defining first, second and third chambers within the housing;
• the first and second chambers in fluid communication with the third chamber and a first one-way valve positioned between the second chamber and the third chamber and a second one-way valve positioned between a treating chemistry inlet and the second chamber;
• wherein the piston is selectively controllable to move between a first position and a second position:
• wherein in the first position, substantially none of a first fluid in the first chamber is directed into the third chamber;
• wherein in the second position, a volume of the first chamber is expanded and substantially all of the first fluid in the first chamber is directed into the third chamber and a volume of the second chamber is contracted causing a second fluid from the second chamber to enter the third chamber and be mixed in the third chamber with the first fluid from the first chamber;
• and
• wherein an additional second fluid is drawn into the second chamber via the second one-way valve when a spring moves the piston from the second position to the first position.