... G1/4 the tooth type structures, unions, more convenient, can match fast by type nut and pipe plug 3 ... the positive, black: negative, yellow: pulse signal Water flow sensor (water flow sensor) and flow switch (flow switch) outlet terminals installation ... two kind of material, mainly for the water heater, wall-hang boiler, water machine. NOTE: OKD-HZ41FA water immersion sensor Campus water flow sensor