KEEPS AN EYE ON YOUR WATER LEVEL SO YOU DON'T HAVE TO. Easy assembly and adjustable to your desired water level. The supply water stays on at all times when the Pool Sentry is in the pool. As the float drops, the water turns on. When the float reaches its set height, the water shuts off. Because the hose is under constant water pressure, it is essential to use a heavy-duty, reinforced garden hose (not included). Rated to 200 psi working pressure and 750 psi burst strength.