A valve for conveying fluid, the valve comprising: a body that is integrally formed and defines a plurality of ports , and defining a plurality of voids , wherein the plurality of voids include cylindrical voids that have a central axis parallel to and collinear with a longitudinal axis of the body ; a bonnet secured to the body and defining a bonnet void; a diaphragm compressed between the bonnet and the body ; a first spring disposed in the bonnet void and configured to bias the diaphragm in a downward direction; and a spindle unit confined in the plurality of voids of the body , wherein the spindle unit comprises: a second spring configured to bias the spindle unit upwardly; a pin and a first seat disc , wherein the first seat disc is configured to contact the pin , and wherein the plurality of ports comprise a first port , a second port , and a third port ; a second seat disc and a seat , wherein the pin is inserted into the second seat disc , wherein the second spring is received by the second seat disc to capture the second spring between the second seat disc and the body ; a guide threaded into the body and bearing on the first seat disc to longitudinally align the first seat disc along the longitudinal axis of the body ; and a seat screw threaded into the body and inwardly bearing on the pin , wherein the seat screw and the pin define a fluid passage in fluid communication with the second port . a body that is integrally formed and defines a plurality of ports , and defining a plurality of voids , wherein the plurality of voids include cylindrical voids that have a central axis parallel to and collinear with a longitudinal axis of the body ; a bonnet secured to the body and defining a bonnet void; a diaphragm compressed between the bonnet and the body ; a first spring disposed in the bonnet void and configured to bias the diaphragm in a downward direction; and a spindle unit confined in the plurality of voids of the body , wherein the spindle unit comprises: a second spring configured to bias the spindle unit upwardly; a pin and a first seat disc , wherein the first seat disc is configured to contact the pin , and wherein the plurality of ports comprise a first port , a second port , and a third port ; a second seat disc and a seat , wherein the pin is inserted into the second seat disc , wherein the second spring is received by the second seat disc to capture the second spring between the second seat disc and the body ; a guide threaded into the body and bearing on the first seat disc to longitudinally align the first seat disc along the longitudinal axis of the body ; and a seat screw threaded into the body and inwardly bearing on the pin , wherein the seat screw and the pin define a fluid passage in fluid communication with the second port . a second spring configured to bias the spindle unit upwardly; a pin and a first seat disc , wherein the first seat disc is configured to contact the pin , and wherein the plurality of ports comprise a first port , a second port , and a third port ; a second seat disc and a seat , wherein the pin is inserted into the second seat disc , wherein the second spring is received by the second seat disc to capture the second spring between the second seat disc and the body ; a guide threaded into the body and bearing on the first seat disc to longitudinally align the first seat disc along the longitudinal axis of the body ; and a seat screw threaded into the body and inwardly bearing on the pin , wherein the seat screw and the pin define a fluid passage in fluid communication with the second port . <EOS>