Having trouble with flow meter still showing value when not running

General
5

Not tested, but this might get you started:

SYSTEM_THREAD(ENABLED)

unsigned long interval =   60 * 60 * 1000;   // How often to Pump the Water
unsigned long previousMillis =      0   ;    // store last Pumping Time
volatile int waterPulse =   0;               // Pulse Counter
int targetPulse         =  8228;             //  8228 Pulses = 1 Gallon.  Verify with a pump test

void setup() {
  Serial.begin(9600);

  // Flow Meter
  pinMode(D6, INPUT_PULLUP);         // THE WATER METER 
  attachInterrupt(D6, flow, FALLING);   // Interrupt for Water Meter
}  // End Setup

void loop() {

  if (millis()  - previousMillis >= interval) {
    pumpWater();      // Pump the Water Down
  }
} // End LOOP


void pumpWater() {
  previousMillis = millis();
  // Turn ON your Pump Here
  while ( waterPulse <=  targetPulse  )    {
    Particle.process();
  }
  // Turn off your Pump Here
  waterPulse = 0;   // reset the pulse counter
}



void flow ()   //  ISR
{
  waterPulse++;
}