drain.py

import RPi.GPIO as GPIO
import time

class TankDrain:
    def __init__(self):
        GPIO.setwarnings(False)
        GPIO.setmode(GPIO.BOARD)

        GPIO.setup(29, GPIO.IN)
        GPIO.setup(31, GPIO.IN)
        GPIO.setup(33, GPIO.IN)
        GPIO.setup(35, GPIO.IN)
        GPIO.setup(37, GPIO.IN)

        GPIO.setup(40, GPIO.OUT)


        self.sum = GPIO.input(29) + GPIO.input(31) + GPIO.input(33) + GPIO.input(35) + GPIO.input(37)

        while self.sum > 0:
            GPIO.output(40, GPIO.HIGH)
            self.sum = GPIO.input(29) + GPIO.input(31) + GPIO.input(33) + GPIO.input(35) + GPIO.input(37)
            time.sleep(6.5)

        GPIO.output(40, GPIO.LOW)