Why do you feel it necessary to recalculate a bunch of constants in loop()?
double P_SETPOINT = .0008;
int A_SETPOINT;
int deadtime=8000;
A_SETPOINT = 972.07*pow(.0008,.0926);
int UCL = A_SETPOINT+6;
double P_UCL = 3*pow(10,-32)*pow(UCL,10.503)+.01;
int LCL = A_SETPOINT-6;
double P_LCL = 3*pow(10,-32)*pow(LCL,10.503)+.01;
These are never going to take on different values, are they?
Make them global, and compute the values in setup().
Analog = analogRead(0);
And Analog contains? Lousy name, by the way. There is something attached to this pin that should give a clue as to the correct name for the value. I'll bet that the clue does not lead to the name Analog.
int Analog;
Analog = analogRead(0);
digitalWrite(3,LOW); //Conductivity Sensor
Lovely. Another variable of the same name in the if block. This leads to baldness.
double Sal;
Lovely. Another Sal. Good to have two Sals around. Easy to keep them straight. Sal is the one with the blond hair.
Back to the drawing board...