Our pool has an electronic water fill device, when the pool level drops, the sensor will open a solenoid valve to let water in. The water is from the backyard water supply that also feeds the sprinkler system, the output from the solenoid valve is connected to the water return right after the pool heater with a T-joint, since there isn't a separate return line from the solenoid valve into the pool, I am worried that when the valve is open, the pool water can backflow into the house. The water pressure at the filter is about 15 psi, what is the psi of a typical city water supply, will it be large enough to prevent backflow? Maybe I should install a check valve to prevent back flow, or am I worrying too much?